Stop crash on multiple attachment selected

Fixed #5272
Closes #5440
// FREEBIE

src/org/thoughtcrime/securesms/ConversationActivity.java

@@ -1059,6 +1059,7 @@ public class ConversationActivity extends PassphraseRequiredActionBarActivity
   }
 
   private void setMedia(Uri uri, MediaType mediaType) {
+    if (uri == null) return;
     attachmentManager.setMedia(masterSecret, uri, mediaType, getCurrentMediaConstraints());
   }