main: Avoid a warning
authorMatthias Clasen <mclasen@redhat.com>
Fri, 26 Jun 2020 12:19:32 +0000 (08:19 -0400)
committerMatthias Clasen <mclasen@redhat.com>
Fri, 26 Jun 2020 12:19:32 +0000 (08:19 -0400)
commitf07d304f196267bec8a57615c98ccad46aedb3cf
treed60ac168c39c88615ee3d57357ab83daa29cf283
parent0ef0edfa9a9bb6c1bb25cf5742f3d61afed8e001
main: Avoid a warning

transient-for relationships only exist between
windows, so check that both candidates are such.

Fixes: #2894
gtk/gtkmain.c