Problem Description

When searching for a non-existent block name in the block palette search feature, the search results dropdown disappears completely without providing any visual feedback or message to indicate that no blocks match the search query.

Steps to Reproduce

1. Open Music Blocks v4 at https://musicblocks.sugarlabs.org/
2. Click the Search icon in the left sidebar (magnifying glass icon)
3. Type a non-existent block name (e.g., "zzzznonexistent", "xyz", or "123")
4. Observe: The search results dropdown disappears
5. Notice: There is NO "No results found" message or empty state indicator

Current Behavior

• Search input accepts text without issue
• Dropdown results disappear when no matches are found
• Sidebar shows only category names
• No message or visual indicator explains the empty state
• Users must clear search manually to resume normal view

Expected Behavior

• Display a clear "No results found" message or empty state indicator
• Show helpful text like: "0 blocks match 'zzzznonexistent'"
• Maintain a visible dropdown or notification area
• Optionally suggest popular search terms
• Provide clear guidance on how to proceed

Impact

• Users experience confusion when searching returns no results
• Uncertainty about whether search functionality is working
• Poor user experience for block discovery
• Inconsistent with standard search UI patterns

Acceptance Criteria

• Empty search results show "No results found" message
• Message clearly states search query that returned no matches
• Results area remains visible (doesn't disappear)
• Styling is consistent with Music Blocks UI
• Works for all types of search queries