odrs: Use local rating if the server has none

This fixes the issue where you are the first reviewer of an app but browsing the
categories shows no rating until the server updates and g-s downloads the ratings
summary again.
1 job for first-review in 60 minutes (queued for 2 seconds)
Status Job ID Name Coverage
failed #201894


Name Stage Failure
build-gnome-software Build
  Installing       : woff2-1.0.2-2.fc28.x86_64                            13/18 
Running scriptlet: woff2-1.0.2-2.fc28.x86_64 13/18
Installing : webkit2gtk3-plugin-process-gtk2-2.22.5-1.fc28.x86_ 14/18
Installing : webkit2gtk3-2.22.5-1.fc28.x86_64 15/18
Installing : gcr-3.28.0-1.fc28.x86_64 16/18
Installing : gnome-online-accounts-3.28.0-1.fc28.x86_64 17/18
Installing : gnome-online-accounts-devel-3.28.0-1.fc28.x86_64 18/18
Running scriptlet: gnome-online-accounts-devel-3.28.0-1.fc28.x86_64 18/18
Pulling docker image gitlab/gitlab-runner-helper:x86_64-cf91d5e1 ...
ERROR: Job failed: execution took longer than 1h0m0s seconds