[gui] fix crash when using container.property() in non-mediawindows

[phil65]

Quite an old bug: Kodi completely crashes when using container(xx).property(yy) in non-mediawindows (root cause: non-mediawindow is casted to CGUIMediaWindow)

Example crash trigger: phil65/skin.estuary@e259a49

Atm container.property() can only work for media windows because our CGUIBaseContainer class only carries a vector of listitems, and not a CFileItemList object.

EDIT: appended a second commit for container(xx).content crash, same reason as above.

[BigNoid]

I don't think there's Container(xx).Property(yy) functionality? In that example commit you replace Container.ListItem.Property with Container.Property. I thought the recent additions allowed you to omit the container part, not the listitem part.

EDIT:
I see there's Container.Property(addoncategory) and Container.Property(reponame)
Nvm than, it was just that the crash commit looks wrong, but that's just for testing.

[phil65]

Yeah that example is just there to have a test case, it doesn't make any sense in terms of functionality.

[phil65]

jenkins build this please.