* app/paint-funcs/paint-funcs.c (initial_sub_region): Fixed
  another bug in initialising the compositing context for the
  special case of dissolve mode.  A further attempt to fix bug
  #121438.

* app/composite/gimp-composite-generic.c
  (gimp_composite_dissolve_any_any_any_generic): Fixed bug in
  calculating whether the destination has an alpha channel (or
  not).