trace_processor: Uncomment code

Broke gcc by committing commented out code.  Revert that change.

Change-Id: I781fc5bfe63ae9ae842022dce702c5c0c3892170
diff --git a/src/trace_processor/trace_processor_shell.cc b/src/trace_processor/trace_processor_shell.cc
index b795bea..342613d 100644
--- a/src/trace_processor/trace_processor_shell.cc
+++ b/src/trace_processor/trace_processor_shell.cc
@@ -589,13 +589,13 @@
       continue;
     }
 
-    // if (has_output) {
-    //  PERFETTO_ELOG(
-    //      "More than one query generated result rows. This is "
-    //      "unsupported.");
-    //  is_query_error = true;
-    //  break;
-    //}
+    if (has_output) {
+      PERFETTO_ELOG(
+          "More than one query generated result rows. This is "
+          "unsupported.");
+      is_query_error = true;
+      break;
+    }
     status = PrintQueryResultAsCsv(&it, output);
     has_output = true;