Using Map Function in React on a Counter Function

I'm trying to use a counter that is being passed a prop that decrements by one for each iteration. It maps through a fake data service with key: value pairs. One of the pairs includes a property of count: 124. I keep getting this error however: "index.js:1 Warning: Failed prop type: Invalid prop keg of type array supplied to KegDetail, expected object."

Also, I want to implement a way that the counter cannot go negative.

Here is the masterKegList:

import { v4 } from 'uuid';

const masterKegList = [
  {
    id: v4(),
    name: 'Hefeweizen',
    brand: 'Widmer',
    price: '$140',
    alcohol: '5%',
    count: 1,
  },
  {
    id: v4(),
    name: 'A Little Sumpin Sumpin',
    brand: 'Lagunitas',
    price: '$160',
    alcohol: '7.5%',
    count: 124
  },
  {
    id: v4(),
    name: 'Chocolate Stout Nitro',
    brand: 'Rogue',
    price: '$220',
    alcohol: '5.8%',
    count: 124,
  },
  {
    id: v4(),
    name: 'Organic Dry Cider',
    brand: 'Avid Cider Co.',
    price: '$180',
    alcohol: '6%',
    count: 124
  },
  {
    id: v4(),
    name: 'Vienna Lager',
    brand: 'pFriem',
    price: '$155',
    alcohol: '5.3%',
    count: 124
  }
];

export function FakeKegList(){
    return masterKegList;
} 

Below is the main component that holds state.

import React from 'react';
import NewKegForm from '../NewKegForm/NewKegForm';
import KegList from "../KegList/KegList";
import KegDetail from "../KegDetail/KegDetail";
import EditKegForm from '../EditKegForm/EditKegForm';
import { FakeKegList } from '../../data/fakeKegService';
import './KegControl.css';
import hefImg from './img/hef.jpg';
import lagunitasImg from './img/lagunitas.jpg';
import rogueImg from './img/rogue.jpg';
import avidImg from './img/avid.jpeg';
import pfriemImg from './img/pfriem.png';
import tapGif from './img/tap.gif';
import pabstImg from './img/pabst.jpg';
import guinnessImg from './img/guinness.jpg';
import pacificoImg from './img/pacifico.jpg';
import Reveal from 'react-reveal/Reveal';
import Button from 'react-bootstrap/Button';


class KegControl extends React.Component {

  constructor(props) {
    super(props);
    this.state = {
      formVisibleOnPage: false,
      masterKegList: FakeKegList([]),
      selectedKeg: null,
      editing: false,
    };

  }

  handleClick = () => {
   if (this.state.selectedKeg != null) {
      this.setState({
        formVisibleOnPage: false,
        selectedKeg: null,
        editing: false
      });
    } else {
      this.setState(prevState => ({
        formVisibleOnPage: !prevState.formVisibleOnPage,
      }));
    }
  }

  handleAddingNewKegToList = (newKeg) => {
    const newMasterKegList = this.state.masterKegList.concat(newKeg);
    this.setState({masterKegList: newMasterKegList,
      formVisibleOnPage: false
    });
  }

  handleChangingSelectedKeg = (id) => {
    const selectedKeg = this.state.masterKegList.filter(keg => keg.id === id)[0];
    this.setState({selectedKeg: selectedKeg});
  }


handleEditClick = () => {
  this.setState({editing: true});
}

handleEditingKegInList = (kegToEdit) => {
  const editedMasterKegList = this.state.masterKegList
    .filter(keg => keg.id !== this.state.selectedKeg.id)
    .concat(kegToEdit);
  this.setState({
      masterKegList: editedMasterKegList,
      editing: false,
      selectedKeg: null
    });
}


handleDeletingKeg = (id) => {
  const newMasterKegList = this.state.masterKegList.filter(keg => keg.id !== id);
  this.setState({
    masterKegList: newMasterKegList,
    selectedKeg: null
  });
}

handleDecrementPint = () => {
  const sellPint = this.state.masterKegList.map((pint) => {
    if (pint.id !== this.state.selectedKeg.id) {
      return pint;
    }
    return {

      ...pint,
      count: pint.count - 1,
      // count: pint.count - 1 > 0
      // prevents count from going negative but doesn't work because count becomes a boolean value
    };
  });
  console.log(sellPint)
  // I tried setting selectedKeg to sellPint to keep user on keg detail page after selling pint, but then I get an error saying keg is an invalid prop type of "object". The number also goes away on keg detail page.
  this.setState({ masterKegList: sellPint, editing: false, formVisibleOnPage: true, selectedKeg: sellPint });
}



  render(){

    let currentlyVisibleState = null;
    let buttonText = null;

  if (this.state.editing ) {      
      currentlyVisibleState = <EditKegForm keg = {this.state.selectedKeg} onEditKeg = {this.handleEditingKegInList} onClickingDecrement = {this.handleDecrementPint} onClick={this.handleClick} />
      buttonText = "Return to Keg List"; 
    } else if (this.state.selectedKeg != null) {
      currentlyVisibleState = <KegDetail keg = {this.state.selectedKeg} onClickingDelete = {this.handleDeletingKeg} onClickingEdit = {this.handleEditClick} onClickingDecrement = {this.handleDecrementPint} />
      buttonText = "Return to Keg List";
    } else if (this.state.formVisibleOnPage) { 
      currentlyVisibleState = <NewKegForm onNewKegCreation={this.handleAddingNewKegToList} />;
    } else {
      currentlyVisibleState =
      <KegList kegList={this.state.masterKegList} onKegSelection={this.handleChangingSelectedKeg}/>;
      buttonText = "Add Keg";
    } 
    return (
      <React.Fragment>
      <Reveal>
      <div className="container">
        {currentlyVisibleState}
        <Button variant="primary" onClick={this.handleClick}>{buttonText}</Button>
      </div>
      </Reveal>
      <Reveal>
      <div className="row">
        <div className="column">
          <img alt="" src={lagunitasImg} />
          <img alt="" src={pfriemImg} />
          <img alt="" src={rogueImg} />
          <img alt="" src={tapGif} />
          <img alt="" src={hefImg} />
          <img alt="" src={avidImg} />
          <img alt="" src={tapGif} />
        </div>
        <div className="column">
          <img alt="" src={pabstImg} />
          <img alt="" src={guinnessImg} />
          <img alt="" src={lagunitasImg} />
          <img alt="" src={pacificoImg} />
          <img alt="" src={pfriemImg} />
          <img alt="" src={pabstImg} />
        </div>
        <div className="column">
          <img alt="" src={lagunitasImg} />
          <img alt="" src={pfriemImg} />
          <img alt="" src={rogueImg} />
          <img alt="" src={tapGif} />
          <img alt="" src={hefImg} />
          <img alt="" src={avidImg} />
          <img alt="" src={tapGif} />
        </div>
        <div className="column">
          <img alt="" src={pabstImg} />
          <img alt="" src={guinnessImg} />
          <img alt="" src={lagunitasImg} />
          <img alt="" src={pacificoImg} />
          <img alt="" src={pfriemImg} />
          <img alt="" src={pabstImg} />
        </div>
      </div>
      </Reveal>
      </React.Fragment>
    );
  }

}

export default KegControl;