Use main looper for key selection

app/src/main/java/eu/faircode/email/Helper.java

@@ -42,6 +42,7 @@ import android.os.Bundle;
 import android.os.Environment;
 import android.os.Handler;
 import android.os.LocaleList;
+import android.os.Looper;
 import android.os.Parcel;
 import android.os.PowerManager;
 import android.os.StatFs;
@@ -1412,7 +1413,7 @@ public class Helper {
 
     static void selectKeyAlias(final Activity activity, final LifecycleOwner owner, final String alias, final IKeyAlias intf) {
         final Context context = activity.getApplicationContext();
-        final Handler handler = new Handler();
+        final Handler handler = new Handler(Looper.getMainLooper());
 
         new Thread(new Runnable() {
             @Override