Fix an NPE in invalid-null-aware-operator-after-short-circuit

Change-Id: I91ebe5b4c511d74be566ce1f01ae0dba07313057
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/154720
Reviewed-by: Konstantin Shcheglov <[email protected]>
Commit-Queue: Brian Wilkerson <[email protected]>

Author: bwilkerson

pkg/analyzer/lib/src/generated/error_verifier.dart

@@ -4225,7 +4225,7 @@ class ErrorVerifier extends RecursiveAstVisitor<void> {
         }
       } else if (target is MethodInvocation) {
         var operator = target.operator;
-        var type = operator.type;
+        var type = operator?.type;
         if (type == TokenType.QUESTION_PERIOD) {
           var realTarget = target.realTarget;
           if (_isExpressionWithType(realTarget)) {

pkg/analyzer/test/src/diagnostics/invalid_null_aware_operator_test.dart

@@ -50,6 +50,22 @@ void f(String? s) {
     ]);
   }
 
+  Future<void> test_methodInvocation_noTarget() async {
+    await assertErrorsInCode('''
+class C {
+  C? m1() => this;
+  C m2() => this;
+  void m3() {
+    m1()?.m2()?.m2();
+  }
+}
+''', [
+      error(StaticWarningCode.INVALID_NULL_AWARE_OPERATOR_AFTER_SHORT_CIRCUIT,
+          75, 2,
+          contextMessages: [message('/test/lib/test.dart', 69, 2)]),
+    ]);
+  }
+
   Future<void> test_methodInvocation_previousTarget() async {
     await assertErrorsInCode('''
 void f(String? s) {