[Vala] [Bug] Compact class as user data need to be passed as unowned

[Tal Hadad <tal_hd hotmail com>]

When I pass lambda method in non-static compact class method
block, I get this error:
error: duplicating SerializedVbo instance, use unowned variable or explicitly invoke copy method

The reason is that the compact class instance is in the user data,
but it's not marked as unowned.

Vala shell threat it as unowned.

Yours,
Tal