bool = cfontface:IsNull()
True if the font face is NULL, i.e. invalid. If functions
that allocate font faces fail, they might not throw an error but simply set the
font face to NULL. You can use this function to check if font face allocation has
failed in which case the font face will be NULL.
Also, certain getter functions can return a NULL object in case the object
doesn't exist. You can use this function to check if a getter function returned
a NULL handle.
True if the font face is NULL, otherwise False