ENH: UnaryRpcHandler: return false on error

src/caosdb/unary_rpc_handler.cpp

@@ -83,6 +83,7 @@ bool UnaryRpcHandler::OnNext(bool ok) {
       // with the fail-fast option. (Note that async unary RPCs don't post a CQ
       // tag at this point, nor do client-streaming or bidi-streaming RPCs that
       // have the initial metadata corked option set.)"
+      return false;
     }
 
     return true;