gtkglsink: fix crash when widget is resized after element destruction

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

Fix #632
20 jobs for backport-mr-274-into-1.16-gtkglsink in 110 minutes and 33 seconds (queued for 48 seconds)
Status Job ID Name Coverage
  Preparation
passed #487198
gst indent

00:00:35

passed #487197
manifest

00:00:51

 
  Build
passed #487204
build cerbero android universal

00:09:02

passed #487205
build cerbero cross win32

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passed #487206
build cerbero cross win64

00:05:54

passed #487203
build cerbero fedora x86_64

00:06:32

passed #487208
gst-ios-12.2
build cerbero ios universal

00:44:59

passed #487207
gst-macos-10.14
build cerbero macos x86_64

00:09:27

passed #487498
build fedora x86_64

00:04:34

passed #487200
build nodebug fedora x86_64

00:05:24

passed #487201
build static fedora x86_64

00:12:14

passed #487499
build static nodebug fedora x86_64

00:11:33

failed #487199
build fedora x86_64

00:03:22

failed #487202
build static nodebug fedora x86_64

00:14:06

 
  Test
passed #487209
check fedora

00:04:00

passed #487210
integration testsuites fedora

00:10:30

passed #487212
valgrind bad

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passed #487213
valgrind ges

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passed #487211
valgrind good

00:09:53

 
  Integrate
passed #487214
android universal examples

00:08:12