Fix migration context data

[KN4CK3R]

The migration page misses some context data if an error occurs.

Without error:

With error:

[codecov-io]

Codecov Report

Merging #14910 (dac3a02) into master (9b261f5) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master   #14910      +/-   ##
==========================================
- Coverage   42.13%   42.13%   -0.01%     
==========================================
  Files         774      774              
  Lines       82905    82906       +1     
==========================================
- Hits        34932    34930       -2     
  Misses      42298    42298              
- Partials     5675     5678       +3     

Impacted Files	Coverage Δ
routers/repo/migrate.go	40.42% <100.00%> (+0.42%)	⬆️
modules/util/timer.go	42.85% <0.00%> (-42.86%)	⬇️
services/pull/pull.go	41.60% <0.00%> (-0.49%)	⬇️
models/unit.go	49.31% <0.00%> (+2.73%)	⬆️

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