Fix class cast exception

[josephtarbit]

Fix class cast exception in ExtensionUtil - resolves #19

[thomasulllrich]

There is more than one location in the changed class which needs to be corrected as far as I remember. Can you check it? It should be the same code only in other methods.

[josephtarbit]

There is more than one location in the changed class which needs to be corrected as far as I remember. Can you check it? It should be the same code only in other methods.

Fixed. I doubt this will get merged though as the last commit was 9 years ago... ~~Do you have a zip of your fixed version of the plugin?~~ Edit: Never mind, finally managed to build it myself