editor: Fix invalid excerpt panic in Editor::hover_links (#40387)

Fixes ZED-17N
Fixes ZED-26Z

Release Notes:

- N/A *or* Added/Fixed/Improved ...

crates/editor/src/editor.rs

@@ -3899,6 +3899,9 @@ impl Editor {
                 }
             })
             .collect::<Vec<_>>();
+        if selection_ranges.is_empty() {
+            return;
+        }
 
         let ranges = match columnar_state {
             ColumnarSelectionState::FromMouse { .. } => {