Issue #12175: Update XCF version even if layer effects are inactive
This patch attempts to resolve #12175 (closed).
Similar to afc0a6d1, we need to use gimp_drawable_get_filters ()
to
get the total number of filters rather than gimp_drawable_has_filters ()
,
which just returns if any filters in the stack are active/visible.
Because of this, we weren't updating the XCF version to 22 when we saved a file that had all of its layer effects set to invisible/inactive.