Fix calling PIP stuck when calls ends on device lock screen.

Fixes #11090

app/src/main/java/org/thoughtcrime/securesms/WebRtcCallActivity.java

@@ -140,7 +140,7 @@ public class WebRtcCallActivity extends BaseActivity implements SafetyNumberChan
     Log.i(TAG, "onPause");
     super.onPause();
 
-    if (!isInPipMode()) {
+    if (!isInPipMode() || isFinishing()) {
       EventBus.getDefault().unregister(this);
     }
 
@@ -157,7 +157,9 @@ public class WebRtcCallActivity extends BaseActivity implements SafetyNumberChan
     Log.i(TAG, "onStop");
     super.onStop();
 
-    EventBus.getDefault().unregister(this);
+    if (!isInPipMode() || isFinishing()) {
+      EventBus.getDefault().unregister(this);
+    }
 
     if (!viewModel.isCallStarting()) {
       CallParticipantsState state = viewModel.getCallParticipantsState().getValue();
@@ -167,6 +169,12 @@ public class WebRtcCallActivity extends BaseActivity implements SafetyNumberChan
     }
   }
 
+  @Override
+  protected void onDestroy() {
+    super.onDestroy();
+    EventBus.getDefault().unregister(this);
+  }
+
   @Override
   public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
     Permissions.onRequestPermissionsResult(this, requestCode, permissions, grantResults);