editor: Fix panic when editor::SelectLargerSyntaxNode overflows excerpt in multi buffer (#25585)

Closes #25513

This PR handles case when `editor::SelectLargerSyntaxNode` expands
across excerpt boundaries and eventually crashes in multi buffer.

Release Notes:

- Fixed panic caused when `editor::SelectLargerSyntaxNode` is called
repetedly in multi buffer.

Co-authored-by: Ben Kunkle <ben.kunkle@gmail.com>

crates/editor/src/editor.rs

@@ -132,7 +132,7 @@ pub use multi_buffer::{
 };
 use multi_buffer::{
     ExcerptInfo, ExpandExcerptDirection, MultiBufferDiffHunk, MultiBufferPoint, MultiBufferRow,
-    ToOffsetUtf16,
+    MultiOrSingleBufferOffsetRange, ToOffsetUtf16,
 };
 use project::{
     lsp_store::{CompletionDocumentation, FormatTrigger, LspFormatTarget, OpenLspBufferHandle},
@@ -10738,7 +10738,10 @@ impl Editor {
                 while let Some((node, containing_range)) = buffer.syntax_ancestor(new_range.clone())
                 {
                     new_node = Some(node);
-                    new_range = containing_range;
+                    new_range = match containing_range {
+                        MultiOrSingleBufferOffsetRange::Single(_) => break,
+                        MultiOrSingleBufferOffsetRange::Multi(range) => range,
+                    };
                     if !display_map.intersects_fold(new_range.start)
                         && !display_map.intersects_fold(new_range.end)
                     {