fix issue #2782 that orm builder generate incorrect sql in some case

[Agzer0]

fix issues #2782 : When ORM is constructing multiple SQL conditions, the OmitEmpty option is used. If the first condition is empty conditions and the second condition is the compound condition. At this time, when there is still a third condition, the generated SQL is wrong.

[gqcn]

@Agzer0 Thanks for your contribution, but please commit associated unit testing case for this update. Please add the unit testing case here: https:/gogf/gf/blob/master/contrib/drivers/mysql/mysql_issue_test.go . There're reference cases already for you.

[codecov-commenter]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (4ad508c) 79.15% compared to head (eff41ee) 79.15%.

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Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2787   +/-   ##
=======================================
  Coverage   79.15%   79.15%           
=======================================
  Files         632      632           
  Lines       52174    52174           
=======================================
+ Hits        41298    41300    +2     
+ Misses       8830     8828    -2     
  Partials     2046     2046           

Flag	Coverage Δ
go-1.15-386	79.17% <100.00%> (-0.01%)	⬇️
go-1.15-amd64	79.16% <100.00%> (-0.04%)	⬇️
go-1.16-386	79.17% <100.00%> (ø)
go-1.16-amd64	79.17% <100.00%> (-0.01%)	⬇️
go-1.17-386	79.17% <100.00%> (+<0.01%)	⬆️
go-1.17-amd64	79.16% <100.00%> (+<0.01%)	⬆️
go-1.18-386	78.78% <100.00%> (-0.01%)	⬇️
go-1.18-amd64	78.78% <100.00%> (?)
go-1.19-386	79.16% <100.00%> (?)
go-1.19-amd64	79.16% <100.00%> (ø)
go-1.20-386	79.14% <100.00%> (?)
go-1.20-amd64	79.13% <100.00%> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
database/gdb/gdb_model_builder.go	97.29% <100.00%> (ø)

... and 1 file with indirect coverage changes

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[Agzer0]

okay, i`ve added testing case