rn,conference: show lonely experience only after joining

Showing the modal earlier is weird because it will be closed as soon as we
connect. Also, we don't know if we are going to be alone until we join.

react/features/conference/components/native/LonelyMeetingExperience.js

@@ -126,11 +126,12 @@ class LonelyMeetingExperience extends PureComponent<Props> {
  */
 function _mapStateToProps(state): $Shape<Props> {
     const { disableInviteFunctions } = state['features/base/config'];
+    const { conference } = state['features/base/conference'];
     const flag = getFeatureFlag(state, INVITE_ENABLED, true);
 
     return {
         _isInviteFunctionsDiabled: !flag || disableInviteFunctions,
-        _isLonelyMeeting: getParticipantCount(state) === 1,
+        _isLonelyMeeting: conference && getParticipantCount(state) === 1,
         _styles: ColorSchemeRegistry.get(state, 'Conference')
     };
 }