Only upload videos to edx if the collection defines course ID

[collinpreston]

Pre-Flight checklist

• [x] Testing
  • [x] Code is tested
  • [x] Changes have been manually tested

What's this PR do?

Fixes an issue where OVS would attempt to register videos with edx even if the collection the video was uploaded to did not define a course ID.

How should this be manually tested?

1. Follow the readme to setup OVS and edx locally.
2. Create a collection but do not define a course ID for the collection.
3. Upload a video to the collection.
4. Verify that the logs for OVS do not show "This video file cannot be added to edX".

It is also worth confirming that you can reproduce the error locally by taking the master branch of OVS and repeating the steps above in order to verify that is "This video file cannot be added to edX" is output to the OVS logs.

Also verify that, with a course ID defined for the collection, uploaded videos are registered with edx.

[codecov-commenter]

Codecov Report

Merging #1028 (b75bcb8) into master (9b0292d) will not change coverage. The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #1028   +/-   ##
=======================================
  Coverage   95.98%   95.98%           
=======================================
  Files         182      182           
  Lines        7356     7356           
  Branches      254      254           
=======================================
  Hits         7061     7061           
  Misses        261      261           
  Partials       34       34           

Impacted Files	Coverage Δ
ui/signals.py	98.07% <100.00%> (ø)

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