gtkglsink: fix crash when widget is resized after element destruction

Prevent _size_changed_cb() to be called after gtkglsink has been finalized.

Fix #632
19 jobs for gtkglsink in 68 minutes and 20 seconds (queued for 1 minute and 14 seconds)
Status Job ID Name Coverage
  Preparation
passed #449195
gst indent

00:00:48

passed #449194
manifest

00:00:43

 
  Build
passed #449201
build cerbero android universal

00:11:34

passed #449202
build cerbero cross win32

00:07:06

passed #449203
build cerbero cross win64

00:06:27

passed #449200
build cerbero fedora x86_64

00:10:26

manual #449205
gst-ios-12.2 allowed to fail manual
build cerbero ios universal
passed #449204
gst-macos-10.14
build cerbero macos x86_64

00:06:46

passed #449196
build fedora x86_64

00:07:20

passed #449197
build nodebug fedora x86_64

00:07:09

passed #449198
build static fedora x86_64

00:14:23

passed #449199
build static nodebug fedora x86_64

00:25:01

 
  Test
passed #449206
check fedora

00:04:44

passed #449207
integration testsuites fedora

00:31:26

passed #449209
valgrind bad

00:07:55

passed #449210
valgrind ges

00:05:42

passed #449208
valgrind good

00:11:39

 
  Integrate
passed #449211
android universal examples

00:05:25

passed #449212
documentation

00:04:23