Do not crash if we try to access an item outside of the bounds of the conversation.

app/src/main/java/org/thoughtcrime/securesms/conversation/ConversationAdapter.java

@@ -387,7 +387,13 @@ public class ConversationAdapter
       if (pagingController != null) {
         pagingController.onDataNeededAroundIndex(correctedPosition);
       }
-      return super.getItem(correctedPosition);
+
+      if (correctedPosition < getItemCount()) {
+        return super.getItem(correctedPosition);
+      } else {
+        Log.d(TAG, "Could not access corrected position " + correctedPosition + " as it is out of bounds.");
+        return null;
+      }
     }
   }