fix #1066

[eleztian]

use default value or "0001-01-01 00:00:00" when time is zero

[codecov-io]

Codecov Report

Merging #1147 into master will decrease coverage by 0.00%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master    #1147      +/-   ##
==========================================
- Coverage   54.30%   54.30%   -0.01%     
==========================================
  Files          41       41              
  Lines        7564     7566       +2     
==========================================
+ Hits         4108     4109       +1     
- Misses       2937     2939       +2     
+ Partials      519      518       -1     

Impacted Files	Coverage Δ
engine.go	61.59% <0.00%> (-0.14%)	⬇️
xorm.go	66.15% <0.00%> (+1.53%)	⬆️

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