Fix nil panic

[mjh1]

While testing locally I noticed that this line was panic'ing on localSourceFile.Name()

[codecov]

Codecov Report

Merging #903 (a220115) into main (0a68878) will decrease coverage by 0.11978%.
Report is 8 commits behind head on main.
The diff coverage is 1.66667%.

@@                 Coverage Diff                 @@
##                main        #903         +/-   ##
===================================================
- Coverage   51.00439%   50.88461%   -0.11978%     
===================================================
  Files             63          63                 
  Lines           6372        6387         +15     
===================================================
  Hits            3250        3250                 
- Misses          2858        2873         +15     
  Partials         264         264                 

Files	Coverage Δ
pipeline/ffmpeg.go	35.52124% <0.00000%> (ø)
clients/manifest.go	43.11594% <0.00000%> (+0.15565%)	⬆️
pipeline/coordinator.go	77.67857% <0.00000%> (-1.23299%)	⬇️
video/clip.go	34.64052% <2.22222%> (-2.16504%)	⬇️

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Files	Coverage Δ
pipeline/ffmpeg.go	35.52124% <0.00000%> (ø)
clients/manifest.go	43.11594% <0.00000%> (+0.15565%)	⬆️
pipeline/coordinator.go	77.67857% <0.00000%> (-1.23299%)	⬇️
video/clip.go	34.64052% <2.22222%> (-2.16504%)	⬇️