smurf: Ensure Epoch is set from data even when a reference WCS is supplied

Previously, the Epoch of the output map reflected the epoch associated with
the reference frame rather than the epoch of the data.
(cherry picked from commit c7bbb1b1bf7c8ae83da65b653baf23f47c0a6ef6)
gaia: fix a problem restoring rtd_mark graphics items using the graphics toolbox
(cherry picked from commit 10149bfe4d2b13f936891026abf41f2075b505c8)