☔ Prevent issues if hash is n/a
☔ Prevent issues if hash is n/a

Apparently it can happen that no hash is available for an STL file.
See SERVER-TQ in Sentry.

So let's be a bit more careful here.

Closes #3107

foosel/OctoPrint,Jaesin/OctoPrint,Jaesin/OctoPrint,foosel/OctoPrint,foosel/OctoPrint,Jaesin/OctoPrint,foosel/OctoPrint,Jaesin/OctoPrint