ensure the sync is limited when rejoining without overlap

otherwise gap would be lost. The server should do this already,
but we're just ensuring it is, to be more robust.

src/matrix/room/timeline/persistence/SyncWriter.js

@@ -207,6 +207,10 @@ export class SyncWriter {
                 }
             }
         }
+        if (!timeline.limited) {
+            log.set("force_limited_without_overlap", true);
+            return Object.assign({}, timeline, {limited: true});
+        }
         return timeline;
     }