agent_ui: Treat whitespace-only input as empty in MessageEditor (#55530)

GitGlimpse895 created

Self-Review Checklist:
- [x] I've reviewed my own diff for quality, security, and reliability
- [x] Unsafe blocks (if any) have justifying comments
- [x] The content is consistent with the [UI/UX
checklist](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
- [x] Tests cover the new/changed behavior
- [x] Performance impact has been considered and is acceptable

Closes #54276

Release Notes:
- Fixed: the Send button in the Agent panel no longer activates when
  the message input contains only whitespace (spaces or tabs).

Change summary

crates/agent_ui/src/message_editor.rs | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

Detailed changes

crates/agent_ui/src/message_editor.rs 🔗

@@ -677,7 +677,7 @@ impl MessageEditor {
     }
 
     pub fn is_empty(&self, cx: &App) -> bool {
-        self.editor.read(cx).is_empty(cx)
+        self.editor.read(cx).text(cx).trim().is_empty()
     }
 
     pub fn is_completions_menu_visible(&self, cx: &App) -> bool {