Update VM getPlaygroundData function to remove circular dependency in blockContainer. It wasn't being used by the tests or the playground and it is not an issue with actual project serialization. Update test to stop passing in runtime to blocklyListen function.

src/virtual-machine.js

@@ -210,7 +210,7 @@ class VirtualMachine extends EventEmitter {
         const threadData = this.runtime.threads.filter(thread => thread.target === instance.editingTarget);
         // Remove the target key, since it's a circular reference.
         const filteredThreadData = JSON.stringify(threadData, (key, value) => {
-            if (key === 'target') return;
+            if (key === 'target' || key === 'blockContainer') return;
             return value;
         }, 2);
         this.emit('playgroundData', {

test/integration/stack-click.js

@@ -45,7 +45,7 @@ test('stack click activates the stack', t => {
                     blockContainer.blocklyListen({
                         blockId: blockId,
                         element: 'stackclick'
-                    }, vm.runtime);
+                    });
                 }
             }