Fix Update Failure

[zgover]

Fixes assertion error during plugin updates, see below.

update failed for AnAction(com.github.florent37.Generator) with ID=florent37.JsonSerializable.Generator

java.lang.AssertionError
	at com.intellij.openapi.actionSystem.AnActionEvent.getRequiredData(AnActionEvent.ja///va:221)
	at com.github.florent37.Generator.update(Generator.java:33)
        {...}

[zgover]

Do please actually test this and not just merge...Truthfully I just hoped it would give you a little shove to actively maintain the plugin if you saw community efforts aside from issues. I was in a rush and added a fix from first google result, just got tired of seeing this plugin throwing errors and blinking in the corner of my eye.

Thanks bud!