Potential fix for unittest RDBBtree.SindexInterruptionViaDrop failure

src/rdb_protocol/btree_store.cc

@@ -746,6 +746,8 @@ void store_t::clear_sindex_data(
         if (!found) {
             // The index got dropped by someone else. That's ok, there's nothing left
             // to do for us.
+            sindex_block.reset_buf_lock();
+            txn->commit();
             return;
         }
 
@@ -852,6 +854,8 @@ void store_t::drop_sindex(uuid_u sindex_id) THROWS_NOTHING {
     if (!found) {
         // The index got dropped by someone else. That's ok, there's nothing left for us
         // to do.
+        sindex_block.reset_buf_lock();
+        txn->commit();
         return;
     }