LSIF: Fix empty string bug in git log parsing.

[efritz]

There can be trailing whitespace in git log with ' ' indicating no parent. This isn't accounted for and returns '' rather than undefined causing a check constraint violation.

[codecov]

Codecov Report

Merging #6622 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff            @@
##           master   #6622      +/-   ##
=========================================
+ Coverage    39.1%   39.1%   +<.01%     
=========================================
  Files        1224    1224              
  Lines       62674   62677       +3     
  Branches     6082    6083       +1     
=========================================
+ Hits        24509   24512       +3     
  Misses      35925   35925              
  Partials     2240    2240

Impacted Files	Coverage Δ
lsif/src/shared/xrepo/commits.ts	92.3% <100%> (+0.64%)	⬆️

[felixfbecker]

Interesting, didn't know git put spaces there. Are you sure it was a space and not a trailing newline?

[efritz]

Interesting, didn't know git put spaces there. Are you sure it was a space and not a trailing newline?

The parent is violated, not the commit. To be extra sure I'll make sure to trim empty lines as well.