Fix missing param name in avfilters

1 job for Applications/19.08 in 16 minutes and 14 seconds (queued for 23 minutes and 4 seconds)
Status Name Job ID Coverage
  Build
failed linux stable-kf5-qt5 qt5.12 #20404

00:16:14

 
Name Stage Failure
failed
linux stable-kf5-qt5 qt5.12 Build
[  2%] Built target kiss_fft
[ 2%] Built target doc-index-cache-bz2
[ 3%] Linking CXX shared module mltpreview.so
[ 3%] Built target mltpreview
make: *** [Makefile:141: all] Error 2
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ERROR: Job failed: exit code 1