[FIX] blockdom: fix event_catcher traceback

When a parent component has an empty child with a t-on
and an event is triggered inside the parent, blockdom
checks if there is an event_catcher to call.
Doing so, an empty child would cause an error.

This commit fixes that.

src/runtime/blockdom/event_catcher.ts

@@ -46,7 +46,7 @@ export function createCatcher(eventsSpec: EventsSpec): Catcher {
           const target = ev.target;
           let currentNode: any = self.child.firstNode();
           const afterNode = self.afterNode;
-          while (currentNode !== afterNode) {
+          while (currentNode && currentNode !== afterNode) {
             if (currentNode.contains(target)) {
               return origFn.call(this, ev);
             }