Ignore empty examples directories (don't add to import menu)

packages/node_modules/@node-red/registry/lib/library.js

@@ -51,7 +51,9 @@ function getFlowsFromPath(path) {
                     }
                     i++;
                 })
-
+                if (!result.hasOwnProperty("f")) {
+                    reject(result);
+                }
                 resolve(result);
             })
         });
@@ -63,7 +65,7 @@ function addNodeExamplesDir(module,path) {
     return getFlowsFromPath(path).then(function(result) {
         exampleFlows = exampleFlows||{};
         exampleFlows[module] = result;
-    });
+    }, function() { return; });
 }
 function removeNodeExamplesDir(module) {
     delete exampleRoots[module];