Don't warn about menu <action> handled by callbacks

[sphery <mtdean@…>]

In [19940], one of Nigel's changes included a, "Warning for garbage in menu action." However, it seems to be a little too eager to warn, as it warns about <action>s handled by callbacks.

For example, the <action> for the <button> "Watch Recordings" (in tvmenu.xml of defaultmenu) is "TV_WATCH_RECORDING", which isn't handled in MythThemedMenu::handleAction(), but is handled by TVMenuCallback() in programs/mythfrontend/main.cpp. This means that we get the warning:

2009-02-07 14:07:38.624 Unknown menu action: TV_WATCH_RECORDING

But then we handle TV_WATCH_RECORDING, properly due to the callback code immediately following the warning. The attached patch seems to fix the issue by only warning when there is no callback or when the action isn't handled by a callback, as I would think an action handled by a callback is not garbage.

Thanks to Stuart M. for explaining to me how this is supposed to work.

[paulh]

(In [19996]) Fix the unknown menu action warnings. Patch by sphery. Fixes #6238.

[Nigel]

(In [19997]) For completeness, also warn of bad menu actions here. See #6238