ActionProvider instances may be added to global lookup, helpful for implementing e.g. Run Single regardless of project type. There are now several such instances (see URL): TestNGActionProvider, RunSQLAction, HintsActionProvider, RunJavaws, and (PHP) RunFileActionProvider. As this list grows, more and more classes will need to be loaded just to check enablement of file-sensitive actions.
Bug #102081 comment #25 discusses the issue and gives an idea for an API. The case of TestNGActionProvider indicates that it may be necessary to register a full ActionProvider instance, as some impls may need more than just command × MIME type for isActionEnabled and/or invokeAction; getSupportedActions would probably just be ignored in this case.
This old bug may not be relevant anymore. If you can still reproduce it in 8.2 development builds please reopen this issue.
Thanks for your cooperation,
NetBeans IDE 8.2 Release Boss