[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 Job ID Name Coverage
  Build
passed #203916
docker
build_linux_36

00:11:39

90.0%
passed #203917
docker
build_linux_37

00:11:20

90.0%
passed #203914
macosx
build_macosx_36

00:11:18

90.0%
passed #203915
macosx
build_macosx_37

00:10:59

90.0%