nvenc: Fix GValue leaks

GValue should be freed with g_value_unset()
8 jobs for fix-nvenc-leaks in 22 minutes and 15 seconds (queued for 59 seconds)
Status Job ID Name Coverage
  Preparation
passed #163121
gst indent

00:00:35

passed #163120
manifest

00:00:33

 
  Build
passed #163122
build fedora x86_64

00:06:10

 
  Test
passed #163123
check fedora

00:03:54

 
  Full Builds
passed #163124
build android arm64 api28

00:05:40

passed #163126
build cerbero cross win32

00:10:42

passed #163127
build cerbero cross win64

00:08:15

passed #163125
build cerbero fedora x86_64

00:08:25