remove unsafe null check

app/src/main/java/chat/rocket/android/videoconference/ui/VideoConferenceActivity.kt

@@ -54,7 +54,8 @@ class VideoConferenceActivity : JitsiMeetActivity(), JitsiVideoConferenceView,
         logJitsiMeetViewState("Joined video conferencing", map)
 
     override fun onConferenceTerminated(map: MutableMap<String, Any>?) {
-        if(map!!.containsKey("error")) {
+        if(!map.isNullOrEmpty()){
+            if(map.containsKey("error")) {
                 logJitsiMeetViewState("Terminated video conferencing with error", map)
             }
             else{
@@ -62,6 +63,7 @@ class VideoConferenceActivity : JitsiMeetActivity(), JitsiVideoConferenceView,
                 finishJitsiVideoConference()
             }
         }
+    }
 
     override fun startJitsiVideoConference(url: String, name: String?) {
         var options = JitsiMeetConferenceOptions.Builder()