Ensure Background sync is not stopped when there is an active call, even when the app goes to background.

vector-app/src/main/java/im/vector/app/VectorApplication.kt

@@ -189,11 +189,15 @@ class VectorApplication :
                 fcmHelper.onEnterBackground(activeSessionHolder)
 
                 if (stopBackgroundSync) {
+                    if (webRtcCallManager.currentCall.get() == null) {
                         Timber.i("App entered background: stop any background sync")
                         activeSessionHolder.getSafeActiveSessionAsync {
                             it?.syncService()?.stopAnyBackgroundSync()
                         }
                         stopBackgroundSync = false
+                    } else {
+                        Timber.i("App entered background: there is an active call do not stop background sync")
+                    }
                 }
             }
         })