extract method: allow to extract @NotNull code with missed branches which would be replaced with 'return null' with check on call site (IDEA-120076)

java/java-tests/testData/refactoring/extractMethod/ExitPoints9_after.java

@@ -0,0 +1,32 @@
+class Result {
+    private String _message;
+
+    public Result(String _message) {
+        this._message = _message;
+    }
+}
+
+class Main {
+    public static Result doIt(String name) {
+        Result result;
+
+        Result result = newMethod(name);
+        if (result != null) return result;
+
+        result = new Result("Name is " + name);
+        return result;
+    }
+
+    private static Result newMethod(String name) {
+        Result result;
+        if (name == null) {
+            result = new Result("Name is null");
+            return result;
+        }
+        if (name.length() == 0) {
+            result = new Result("Name is empty");
+            return result;
+        }
+        return null;
+    }
+}