Fix WebRTC capability check for unregistered users

Fixes #6358
Closes #6368
// FREEBIE

src/org/thoughtcrime/securesms/ConversationActivity.java

@@ -974,7 +974,10 @@ public class ConversationActivity extends PassphraseRequiredActionBarActivity
   }
 
   private void initializeBetaCalling() {
-    if (!TextSecurePreferences.isWebrtcCallingEnabled(this) || isGroupConversation()) {
+    if (!TextSecurePreferences.isPushRegistered(this)       ||
+        !TextSecurePreferences.isWebrtcCallingEnabled(this) ||
+        isGroupConversation())
+    {
       return;
     }