avoid IllegalStateException for CallActivity#stopCallingSound

This might happen sometimes. For now it's a try-catch instead trying to control the state of the mediaPlayer which could be quite difficult.

this will avoid the following exception:

    java.lang.IllegalStateException
    	at android.media.MediaPlayer.isPlaying(Native Method)
    	at com.nextcloud.talk.activities.CallActivity.stopCallingSound(CallActivity.java:2640)
    	at com.nextcloud.talk.activities.CallActivity.lambda$setCallState$31$com-nextcloud-talk-activities-CallActivity(CallActivity.java:2583)
    	at com.nextcloud.talk.activities.CallActivity$$ExternalSyntheticLambda7.run(Unknown Source:2)
    	at android.os.Handler.handleCallback(Handler.java:883)
    	at android.os.Handler.dispatchMessage(Handler.java:100)
    	at android.os.Looper.loop(Looper.java:237)
    	at android.app.ActivityThread.main(ActivityThread.java:8167)
    	at java.lang.reflect.Method.invoke(Native Method)
    	at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:496)
    	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1100)

Signed-off-by: Marcel Hibbe <dev@mhibbe.de>

app/src/main/java/com/nextcloud/talk/activities/CallActivity.java

@@ -2593,12 +2593,18 @@ public class CallActivity extends CallBaseActivity {
 
     private void stopCallingSound() {
         if (mediaPlayer != null) {
-            if (mediaPlayer.isPlaying()) {
-                mediaPlayer.stop();
+            try {
+                if (mediaPlayer.isPlaying()) {
+                    mediaPlayer.stop();
+                }
+            } catch (IllegalStateException e) {
+                Log.e(TAG, "mediaPlayer was not initialized", e);
+            } finally {
+                if (mediaPlayer != null) {
+                    mediaPlayer.release();
+                }
+                mediaPlayer = null;
             }
-
-            mediaPlayer.release();
-            mediaPlayer = null;
         }
     }