Почему вылетает приложение при запуске 34 строки?

При запуске андроид-приложения, приложение вылетает, заметил, что вылетает при выполнении 34 строки.

package com.example.svetovor;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.LinearLayout;

public class MainActivity extends AppCompatActivity {
    private LinearLayout first_square, second_square, third_square;
    private Button button_first;
    private boolean start_stop = false;
    private int counter = 0;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        second_square = findViewById(R.id.cecond_square);
        third_square = findViewById(R.id.third_square);
        button_first = findViewById(R.id.button_first);
    }

    public void onClickStart(View view){
        if(!start_stop) {button_first.setText("Stop");
            start_stop = true;

            new Thread(new Runnable() {
                @Override
                public void run() {
                    while (start_stop) {
                        counter++;
                        if(counter == 1) {
                            first_square.setBackgroundColor(getResources().getColor(R.color.gray));
                            first_square.setBackgroundColor(getResources().getColor(R.color.red));
                        } else if (counter == 2) {
                            second_square.setBackgroundColor(getResources().getColor(R.color.gray));
                            second_square.setBackgroundColor(getResources().getColor(R.color.yellow));
                        } else if (counter == 3) {
                            counter = 0;
                            third_square.setBackgroundColor(getResources().getColor(R.color.gray));
                            third_square.setBackgroundColor(getResources().getColor(R.color.green));
                        }
                        try {
                            Thread.sleep(50);
                        } catch (InterruptedException e) {
                            throw new RuntimeException(e);
                        }
                    }
                }
            }).start();
        } else {
            start_stop = false;
            button_first.setText("Start");
        }
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        start_stop = false;
    }
}

activity_main.xml:

    <?xml version="1.0" encoding="utf-8"?>
    <androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:app="http://schemas.android.com/apk/res-auto"
        xmlns:tools="http://schemas.android.com/tools"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        tools:context=".MainActivity">
    
        <LinearLayout
            android:id="@+id/first_square"
            android:layout_width="100dp"
            android:layout_height="100dp"
            android:layout_marginStart="150dp"
            android:layout_marginTop="30dp"
            android:layout_marginEnd="150dp"
            android:layout_marginBottom="600dp"
            android:background="@color/gray"
            android:orientation="horizontal"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent"></LinearLayout>
    
        <LinearLayout
            android:id="@+id/third_square"
            android:layout_width="100dp"
            android:layout_height="100dp"
            android:layout_marginStart="150dp"
            android:layout_marginEnd="150dp"
            android:layout_marginBottom="363dp"
            android:orientation="horizontal"
            android:background="@color/gray"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintHorizontal_bias="0.545"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toBottomOf="@+id/cecond_square"
            app:layout_constraintVertical_bias="1.0">
    
        </LinearLayout>
    
        <LinearLayout
            android:id="@+id/cecond_square"
            android:layout_width="100dp"
            android:layout_height="100dp"
            android:layout_marginStart="150dp"
            android:layout_marginTop="150dp"
            android:layout_marginEnd="150dp"
            android:layout_marginBottom="480dp"
            android:orientation="horizontal"
            android:background="@color/gray"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent" >
    
        </LinearLayout>
    
        <Button
            android:id="@+id/button_first"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginStart="150dp"
            android:layout_marginTop="76dp"
            android:layout_marginEnd="150dp"
            android:layout_weight="1"
            android:onClick="onClickStart"
            android:text="@string/button_1"
            app:cornerRadius="8sp"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintHorizontal_bias="0.478"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toBottomOf="@+id/third_square"
            app:strokeColor="#000"
            app:strokeWidth=

"3sp" />