don't infer ->null contracts in scope of @MethodAreNonNullByDefault (addendum to IDEA-160991)

java/java-tests/testData/inspection/dataFlow/fixture/CustomTypeQualifierDefault.java

@@ -24,10 +24,15 @@ class NotNullClass {
     return <warning descr="'null' is returned by the method declared as @MethodsAreNotNullByDefault">null</warning>;
   }
 
-  private Object privateFoo() {
+  private String privateFoo() {
     return <warning descr="'null' is returned by the method declared as @MethodsAreNotNullByDefault">null</warning>;
   }
 
+  {
+    String s2 = privateFoo();
+    int i2 = s2.length();
+  }
+
   @Nullable
   public Object foo2() {
     return null;