fix #1896

[quentin]

Keep existing objects alive until the end of the MaterializeAggregationQueriesTransformer.

[codecov]

Codecov Report

Merging #2445 (1648eaa) into master (2914f7b) will increase coverage by 0.22%.
Report is 23 commits behind head on master.
The diff coverage is 77.61%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2445      +/-   ##
==========================================
+ Coverage   77.75%   77.98%   +0.22%     
==========================================
  Files         474      483       +9     
  Lines       31164    32012     +848     
==========================================
+ Hits        24232    24964     +732     
- Misses       6932     7048     +116     

Files	Coverage Δ
src/FunctorOps.cpp	60.81% <ø> (ø)
src/RelationTag.h	53.03% <ø> (+0.79%)	⬆️
src/ast/Aggregator.cpp	95.65% <100.00%> (+0.19%)	⬆️
src/ast/Aggregator.h	100.00% <ø> (ø)
src/ast/Attribute.h	100.00% <100.00%> (ø)
src/ast/Component.h	100.00% <ø> (ø)
src/ast/IterationCounter.cpp	100.00% <100.00%> (ø)
src/ast/Lattice.h	100.00% <100.00%> (ø)
src/ast/Program.h	100.00% <ø> (ø)
src/ast/QualifiedName.h	94.11% <ø> (ø)
... and 80 more

... and 6 files with indirect coverage changes

[julienhenry]

Thanks for the fix !