Info activity: manage not scanned / no length medias

Fixes #1032
4 jobs for !251 with infoactivity_improvements in 25 minutes and 21 seconds (queued for 1 second)
detached
Status Job ID Name Coverage
  Build
passed #306435
android debian
build-ml-arm64

00:24:01

passed #306436
android debian
build-ml-armv7

00:22:53

passed #306437
android debian
build-ml-x86

00:24:16

passed #306438
android debian
build-ml-x86_64

00:25:20