Fix method ambiguity detected by Julia v1.3

[blegat]

Closes #854

[codecov-io]

Codecov Report

Merging #891 into master will decrease coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #891      +/-   ##
==========================================
- Coverage    95.1%   95.09%   -0.02%     
==========================================
  Files          80       80              
  Lines        8481     8762     +281     
==========================================
+ Hits         8066     8332     +266     
- Misses        415      430      +15

Impacted Files	Coverage Δ
src/Utilities/model.jl	94.63% <ø> (-0.27%)	⬇️
src/Bridges/Constraint/scalarize.jl	77.55% <0%> (-2.45%)	⬇️
src/Utilities/functions.jl	94.06% <0%> (+0.05%)	⬆️
src/Bridges/bridge_optimizer.jl	95.75% <0%> (+0.15%)	⬆️
src/Bridges/lazy_bridge_optimizer.jl	93.33% <0%> (+0.42%)	⬆️

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