Canvas Panel: Editing background image URL input closes unexpectedly

### What happened? https://github.com/user-attachments/assets/058df139-7798-490f-9001-17c9dbb52596 When editing an element in the Canvas panel and trying to change its background image, if I select 'URL' as the image source and focus on the URL input field, the input dialog suddenly closes as soon as I start typing or paste a URL. This makes it impossible to enter or edit the URL for the background image. ### What did you expect to happen? The input dialog should remain open while typing or pasting a URL in the background image input field, allowing the user to enter the desired URL. ### Did this work before? Not sure – I do not recall if this worked in a previous version. (Please update if you remember a version where it worked.) ### How do we reproduce it? 1. Edit a dashboard with a Canvas panel. 2. Select an element and try to change its background image. 3. Choose 'URL' as the image source. 4. Click into the URL input field and begin typing or paste a URL. 5. Observe that the input dialog closes unexpectedly. ### Is the bug inside a dashboard panel? Yes, the bug appears inside the Canvas dashboard panel. ### Environment (with versions)? Grafana: 11.3.0 OS: Linux Browser: Firefox 143.0.1 (64-bit) ### Grafana platform? Kubernetes ### Datasource(s)? _No response_