Device gives error and then restarts after trying to uninstall application

I'm having a bug with the application I created, the code is compiling normal and no error or warning , and the application is also working on the phone, but when I try to uninstall this application from I get the following message:

  

"The package installer application has stopped."

And in another mobile phone of mine, the application displays the following message:

  

"System interface application stopped"

and then the device simply restarts.

Both phones are MotoG 2nd generation, with android 5.0.2 . I'm sorry for asking such a comprehensive question but I really have no idea why this error occurred. The program is very simple, so I will send the 3 classes in it:

public class Facts {

    public String[] Mfacts = {
            "Ants stretch when they wake up in the morning.",
            "Ostriches can run faster than horses.",
            "Olympic gold medals are actually made mostly of silver.",
            "Samsung is also a full time weapons manufacturer.",
            "Terrafugia is the world's first flying car."};

    //Save the used facts

    public String getFact() {
        //The button was clicked, so update the fact with a new fact
        String fact = "";
        //Randomly select a fact
        Random randomGenerator = new Random(); // Construct a new random generator

        int randomNumber = randomGenerator.nextInt(Mfacts.length);

        fact = Mfacts[randomNumber];
        return fact;

    }

}

public class Colors {

    public String[] mColors = {
            "#39add1", // light blue
            "#3079ab", // dark blue
            "#c25975", // mauve

    };

    public int getColor() {

        //The button was clicked, so update the fact with a new fact
        String color = "";

        //Randomly select a fact
        Random randomGenerator = new Random(); // Construct a new random generator
        int randomNumber = randomGenerator.nextInt(mColors.length);

        color = mColors[randomNumber];
        int colorAsInt = Color.parseColor(color);

        return colorAsInt;
    }
}

public class MainActivity extends Activity {

    private Facts mFactBook = new Facts();
    private Colors mColorWheel = new Colors();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        //Declare our View variables and asisgn the Views from the layout file
        final TextView factLabel = (TextView) findViewById(R.id.factTextView);
        final Button showFactButton = (Button) findViewById(R.id.showFactButton);
        final RelativeLayout relativeLayout = (RelativeLayout) findViewById(R.id.relativeLayout);

        AdView mAdView = (AdView) findViewById(R.id.adView);
        AdRequest adRequest = new AdRequest.Builder().build();
        mAdView.loadAd(adRequest);

        View.OnClickListener listener = new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                String fact = mFactBook.getFact();

                //Update the label with our dynamic fact
                factLabel.setText(fact);

                int color = mColorWheel.getColor();

                relativeLayout.setBackgroundColor(color);

                showFactButton.setTextColor(color);
            }
        };

        showFactButton.setOnClickListener(listener);
        Toast.makeText(this, "Welcome to Fun Facts!!", Toast.LENGTH_LONG).show();

    }
}

And build.gradle app:

android {

    compileSdkVersion 22

    buildToolsVersion "22.0.1"

    defaultConfig {
        applicationId "insight.com.br.funfacts"
        minSdkVersion 14
        targetSdkVersion 22
        versionCode 2
        versionName "1.1"
    }
    buildTypes {
        release {
            minifyEnabled true
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {

    compile fileTree(dir: 'libs', include: ['*.jar'])

    compile 'com.android.support:appcompat-v7:22.2.0'

    compile 'com.google.android.gms:play-services-ads:8.1.0'
}

I'm using adView to do some tests with adMob , is it possible that the problem is related to this?

If you need anything else from the code, just say that I put it here. Many thanks to those who try to help!