main, fix NullPointerException.

app/src/main/java/com/hyperling/apps/infinitetimer/MainActivity.java

@@ -596,15 +596,19 @@ public class MainActivity extends AppCompatActivity {
         String tag = TAG + "playSound";
         if (DEBUG) Log.d(tag, "Starting");
 
-        /* Original code, did not work on Nexus 7 with CM 12.1-20151117 (Android 5.1.1) * /
-        Uri uri = Uri.parse("android.resource://" + getPackageName() + "/raw/chime_sound_7143");
-        //Ringtone ringtone = RingtoneManager.getRingtone(getApplicationContext(), ringtoneUri);
-        Ringtone ringtone = RingtoneManager.getRingtone(getApplicationContext(), uri);
-        ringtone.play();
-        /**/
-
         try {
-            mediaPlayer.start();
+            // Safely instantiate MediaPlayer locally to prevent NPE
+            Uri uri = android.media.RingtoneManager.getDefaultUri(android.media.RingtoneManager.TYPE_NOTIFICATION);
+            MediaPlayer localPlayer = MediaPlayer.create(this, uri);
+            
+            if (localPlayer != null) {
+                localPlayer.start();
+                localPlayer.release(); // Clean up resources immediately
+            } else {
+                // Fallback for edge cases where create() fails
+                android.media.Ringtone ringtone = android.media.RingtoneManager.getRingtone(this, uri);
+                if (ringtone != null) ringtone.play();
+            }
         } catch (Exception e) {
             sharedPreferences.edit().putBoolean(keyStartStop, false).apply();