Flutter - ERROR : No signature of method: build_alrohbcqffdojo30hcvnhe46c.android() is applicable for argument types:

I just set up Firebase in my project and After running the build.gradle task it throws the error. in the title it's error is half full error is :

* What went wrong:
A problem occurred evaluating project ':app'.
> No signature of method: build_alrohbcqffdojo30hcvnhe46c.android() is applicable for argument 
types: (build_alrohbcqffdojo30hcvnhe46c$_run_closure2) values: 
[build_alrohbcqffdojo30hcvnhe46c$_run_closure2@71e64975]

My Android app level code is :

android {
compileSdkVersion 30

compileOptions {
    sourceCompatibility JavaVersion.VERSION_1_8
    targetCompatibility JavaVersion.VERSION_1_8
}

kotlinOptions {
    jvmTarget = '1.8'
}

sourceSets {
    main.java.srcDirs += 'src/main/kotlin'
}

defaultConfig {
    // TODO: Specify your own unique Application ID (https://developer.android.com/studio/build/application-id.html).
    applicationId "com.example.crypto_wallet"
    minSdkVersion 21
    targetSdkVersion 30
    versionCode flutterVersionCode.toInteger()
    versionName flutterVersionName
    multiDexEnable true
}

Any fix for this ERROR ? I'd be thankful. <3