How to use chart.js in nuxt.js?

I made a small app to confirm how to use chart.js in Nuxt.js. My recent project's language is TypeScript, so I tried to make my code in Typescript. and I also have used Nuxt.js as framework. I referred to this site. But my sample code has error occurred.

first of all, I made chart file as .vue file. my chart components made components directory in Nuxt.js. but in this code, error occurred on @Prop. error message and code is below.

"Property 'chartData' has no initializer and is not definitely assigned in the constructor."

    <script lang="ts">
import { Component, Vue, Prop, Watch, mixins } from "nuxt-property-decorator";
import Chart from "chart.js";
import VueChart from "vue-chartjs";
const Line = VueChart.Line;
const reactiveProp = VueChart.mixins.reactiveProp;

@Component
export default class ChartLine extends mixins(Line, reactiveProp) {
  @Prop({ default: {} }) chartData: Chart.ChartData;
  @Prop({ default: {} }) options: Chart.ChartOptions;

  mounted() {
    this.renderChart(this.chartData, this.options);
  }
}
</script>

In pages of Nuxt.js, I made chart.js file as display chart. so, my code is below

    <template>
  <div class="chart-container">
    <ChartLine
      :chartData="chartData"
      :options="chartOption"
      :styles="chartStyles"
    />
  </div>
</template>

<script lang="ts">
import { Component, Vue, Prop } from 'nuxt-property-decorator'
import { ChartData, ChartOptions } from 'chart.js'
import ChartLine from '~/components/ChartLine.vue'

@Component({ components: { ChartLine } })
export default class ChartPage extends Vue {
  private chartData: ChartData = {
    labels: ['A', 'B', 'C', 'D', 'E'],
    datasets: [
      {
        label: 'Data One',
        data: [1, 5, 3, 4, 3],
      },
      {
        label: 'Data Two',
        data: [10, 50, 30, 40, 30],
      },
    ],
  }
  private chartOption: ChartOptions = {
    maintainAspectRatio: false,
  }

  private chartStyles = {
    height: '100%',
    width: '100%',
  }
}
</script>

<style lang="scss">
.chart-container {
  position: relative;
  height: 40vh;
  width: 80vw;
  margin: 0 auto;
}
</style>

I really don't understand how to fix these error. Could anyone advise me?