[widgets][experimenteditor] Use get to test block parameters

If the value was not changed from the default, it won't be
dumped and thus when filtering, it won't be there.
4 jobs for 276_fix_parameter_filter_crash in 11 minutes and 42 seconds (queued for 8 seconds)
Status Name Job ID Coverage
  Build
passed build_linux_36 #203916
docker

00:11:39

90.0%
passed build_linux_37 #203917
docker

00:11:20

90.0%
passed build_macosx_36 #203914
macosx

00:11:18

90.0%
passed build_macosx_37 #203915
macosx

00:10:59

90.0%