playsink: fix audio passthrough hang when set play rate

when audio passthrough is enable, audio_filter will not
put into audiochain. When do reconfigure, playsink will
remove previous audio chain as audio_filter is not match
with chain->filter (should be NULL). Need check whether
chain->filter is valided first to avoid remove audio chain
and cause hang
22 jobs for fix_passthrough_hang in 78 minutes and 53 seconds (queued for 1 second)
latest
Status Job ID Name Coverage
  Preparation
passed #393301
gst indent

00:00:34

passed #393300
manifest

00:00:40

 
  Build
passed #393307
build cerbero android universal

00:10:43

passed #393308
build cerbero cross win32

00:07:07

passed #393309
build cerbero cross win64

00:08:00

passed #393306
build cerbero fedora x86_64

00:06:41

passed #393311
gst-ios-12.2 allowed to fail manual
build cerbero ios universal

00:35:22

passed #393310
gst-macos-10.14
build cerbero macos x86_64

00:07:07

passed #393302
build fedora x86_64

00:08:32

passed #393303
build nodebug fedora x86_64

00:07:16

passed #393304
build static fedora x86_64

00:15:40

passed #393305
build static nodebug fedora x86_64

00:12:41

 
  Test
passed #393312
check fedora

00:03:39

passed #393313
integration testsuites fedora

00:08:50

passed #393317
valgrind bad

00:08:19

passed #393314
valgrind base

00:17:15

passed #393318
valgrind ges

00:07:58

passed #393334
valgrind good

00:07:15

passed #393316
valgrind ugly

00:02:23

failed #393315
valgrind good

00:15:19

 
  Integrate
passed #393319
android universal examples

00:06:55

passed #393320
documentation

00:04:39