Check for payload length

src/console/widget.ts

@@ -222,7 +222,7 @@ class ConsoleWidget extends Widget {
           let content = value.content as KernelMessage.IExecuteOkReply;
           this._inspectionHandler.handleExecuteReply(content);
           // Use deprecated payloads for backwards compatibility.
-          if (content.payload) {
+          if (content.payload && content.payload.length) {
             let setNextInput = content.payload.filter(i => {
               return (i as any).source === 'set_next_input';
             })[0];

src/notebook/notebook/actions.ts

@@ -865,7 +865,7 @@ namespace Private {
           if (reply && reply.content.status === 'ok') {
             let content = reply.content as KernelMessage.IExecuteOkReply;
             parent.inspectionHandler.handleExecuteReply(content);
-            if (content.payload) {
+            if (content.payload && content.payload.length) {
               handlePayload(content, parent, child);
             }
           } else {