The image input for nodes loaded from templates appears empty in the
Properties Panel.
When the widget's current value (saved in the template) is not in the
available file list returned by the server, the selectedSet is empty,
causing a placeholder to be displayed instead of the actual value.
Added a missingValueItem computed property in WidgetSelectDropdown.vue.
When the current value is not in inputItems or outputItems, it creates a
fallback item and adds it to dropdownItems.
┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-8276-fix-default-image-input-for-the-template-is-displayed-as-empty-on-dropdown-selection-2f16d73d3650817eaad5e4e33637fb74)
by [Unito](https://www.unito.io)
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Co-authored-by: Alexander Brown <drjkl@comfy.org>
Co-authored-by: github-actions <github-actions@github.com>