Fix code select for method reference

Consider the following:
```groovy
def maker = String[]::new
```

Code select (Ctrl+click) should not be available for "::" but it is.

![image](https://user-images.githubusercontent.com/18193802/81432384-71ab6a00-9128-11ea-92eb-eae041ebc47e.png)