settings_ui: Last minute cleanup (#40217)

Closes #ISSUE

Release Notes:

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

---------

Co-authored-by: Mikayla <mikayla@zed.dev>

crates/language/src/buffer_tests.rs

@@ -269,7 +269,7 @@ async fn test_first_line_pattern(cx: &mut TestAppContext) {
 async fn test_language_for_file_with_custom_file_types(cx: &mut TestAppContext) {
     cx.update(|cx| {
         init_settings(cx, |settings| {
-            settings.file_types.extend([
+            settings.file_types.get_or_insert_default().extend([
                 ("TypeScript".into(), vec!["js".into()].into()),
                 (
                     "JavaScript".into(),

crates/language/src/language_settings.rs

@@ -639,7 +639,7 @@ impl settings::Settings for AllLanguageSettings {
 
         let mut file_types: FxHashMap<Arc<str>, GlobSet> = FxHashMap::default();
 
-        for (language, patterns) in &all_languages.file_types {
+        for (language, patterns) in all_languages.file_types.iter().flatten() {
             let mut builder = GlobSetBuilder::new();
 
             for pattern in &patterns.0 {
@@ -778,6 +778,7 @@ impl settings::Settings for AllLanguageSettings {
             .project
             .all_languages
             .file_types
+            .get_or_insert_default()
             .extend(associations);
 
         // cursor global ignore list applies to cursor-tab, so transfer it to edit_predictions.disabled_globs