Fix NPE in completion contributor (issue 25711)

pkg/analysis_server/lib/src/services/completion/dart/type_member_contributor.dart

Index: pkg/analysis_server/lib/src/services/completion/dart/type_member_contributor.dart
diff --git a/pkg/analysis_server/lib/src/services/completion/dart/type_member_contributor.dart b/pkg/analysis_server/lib/src/services/completion/dart/type_member_contributor.dart
index 257527b3b8dacce981100fa525b1aee305b82332..7a0f76020fec1538ac517427ef3f02a9cef28dc1 100644
--- a/pkg/analysis_server/lib/src/services/completion/dart/type_member_contributor.dart
+++ b/pkg/analysis_server/lib/src/services/completion/dart/type_member_contributor.dart
@@ -72,7 +72,8 @@ class TypeMemberContributor extends DartCompletionContributor {
         } else if (elem is LocalVariableElement) {
           type = elem.type;
         }
-        if (type.isDynamic && expression is SimpleIdentifier) {
+        if ((type == null || type.isDynamic) &&
+            expression is SimpleIdentifier) {
           // If the element does not provide a good type
           // then attempt to get a better type from a local declaration
           _LocalBestTypeVisitor visitor =