Fix NPE when there is no keyword (issue 26630)

pkg/analysis_server/lib/src/services/correction/assist_internal.dart

Index: pkg/analysis_server/lib/src/services/correction/assist_internal.dart
diff --git a/pkg/analysis_server/lib/src/services/correction/assist_internal.dart b/pkg/analysis_server/lib/src/services/correction/assist_internal.dart
index 244fb3d16bd9d4dc44d6e1246007fb9bb771c0fe..f58469d036c2709916a1b8704125cde9e7601300 100644
--- a/pkg/analysis_server/lib/src/services/correction/assist_internal.dart
+++ b/pkg/analysis_server/lib/src/services/correction/assist_internal.dart
@@ -338,7 +338,7 @@ class AssistProcessor {
     }
     // add edit
     Token keyword = declarationList.keyword;
-    if (keyword.keyword == Keyword.VAR) {
+    if (keyword?.keyword == Keyword.VAR) {
       SourceRange range = rangeToken(keyword);
       _addReplaceEdit(range, typeSource);
     } else {