Fix inferMethodInvocation in the case where interfaceMember is null.

pkg/front_end/lib/src/fasta/type_inference/type_inferrer.dart

Index: pkg/front_end/lib/src/fasta/type_inference/type_inferrer.dart
diff --git a/pkg/front_end/lib/src/fasta/type_inference/type_inferrer.dart b/pkg/front_end/lib/src/fasta/type_inference/type_inferrer.dart
index a44e76fada8c41e63ca20e98eedfc4301a719108..8d7f4bf6f872c93b4a909ea341c452e6d2cf432a 100644
--- a/pkg/front_end/lib/src/fasta/type_inference/type_inferrer.dart
+++ b/pkg/front_end/lib/src/fasta/type_inference/type_inferrer.dart
@@ -808,10 +808,12 @@ abstract class TypeInferrerImpl extends TypeInferrer {
       receiverVariable?.type = receiverType;
     }
     bool isOverloadedArithmeticOperator = false;
-    interfaceMember ??=
-        findMethodInvocationMember(receiverType, desugaredInvocation);
-    methodName ??= desugaredInvocation.name;
-    arguments ??= desugaredInvocation.arguments;
+    if (desugaredInvocation != null) {
+      interfaceMember =
+          findMethodInvocationMember(receiverType, desugaredInvocation);
+      methodName = desugaredInvocation.name;
+      arguments = desugaredInvocation.arguments;
+    }
     if (interfaceMember is Procedure) {
       isOverloadedArithmeticOperator = typeSchemaEnvironment
           .isOverloadedArithmeticOperatorAndType(interfaceMember, receiverType);