Info activity: manage not scanned / no length medias

Fixes #1032
4 jobs for !251 with infoactivity_improvements in 23 minutes and 35 seconds (queued for 1 second)
detached
Status Job ID Name Coverage
  Build
passed #305028
android debian
build-ml-arm64

00:22:22

passed #305029
android debian
build-ml-armv7

00:23:34

passed #305030
android debian
build-ml-x86

00:23:34

passed #305031
android debian
build-ml-x86_64

00:23:33