Add missing error to Doctor log

[jolheiser]

Minimal change, self-explanatory. But it is also fairly important context for the log.

[codecov-commenter]

Codecov Report

Merging #15813 (884a484) into main (3656a2a) will decrease coverage by 0.00%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##             main   #15813      +/-   ##
==========================================
- Coverage   44.00%   44.00%   -0.01%     
==========================================
  Files         680      680              
  Lines       82212    82212              
==========================================
- Hits        36179    36177       -2     
  Misses      40128    40128              
- Partials     5905     5907       +2     

Impacted Files	Coverage Δ
modules/doctor/dbversion.go	42.85% <0.00%> (ø)
models/repo_list.go	77.04% <0.00%> (-0.78%)	⬇️
services/pull/pull.go	43.37% <0.00%> (-0.46%)	⬇️
modules/queue/workerpool.go	52.74% <0.00%> (ø)
modules/log/event.go	59.90% <0.00%> (+0.94%)	⬆️

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[zeripath]

make lgtm work