[backport rh-test] Fix asset browser on subgraph nodes (#6242)

Backport of #6240 to `rh-test`

Automatically created by backport workflow.

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-6242-backport-rh-test-Fix-asset-browser-on-subgraph-nodes-2956d73d36508103880cfedc151a542f)
by [Unito](https://www.unito.io)

Co-authored-by: AustinMroz <austin@comfy.org>

src/renderer/extensions/vueNodes/widgets/composables/useComboWidget.ts

@@ -371,7 +371,7 @@ const addComboWidget = (
       'asset',
       inputSpec.name,
       displayLabel,
-      async () => {
+      async function (this: IBaseWidget) {
         if (!isAssetWidget(widget)) {
           throw new Error(`Expected asset widget but received ${widget.type}`)
         }
@@ -406,7 +406,7 @@ const addComboWidget = (
             }
 
             const oldValue = widget.value
-            widget.value = validatedFilename.data
+            this.value = validatedFilename.data
             node.onWidgetChanged?.(
               widget.name,
               validatedFilename.data,