Fix overlaps

[LePetitTim]

Fix #2465

[gutard]

Il y a un cas qui n'est pas pris en compte (rien à voir avec cette PR, c'était déjà bugué avant), c'est quand l'intersection mélange point et linestring, par ex. GEOMETRYCOLLECTION(POINT(1 1),LINESTRING(1 2,1 1.5))

Je pense qu'il faut plutôt faire NOT ST_IsEmpty(ST_CollectionExtract(ST_intersection(geom, line), 2))

[codecov]

Codecov Report

Merging #2466 (6864067) into master (e8389dc) will increase coverage by 0.00%.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #2466   +/-   ##
=======================================
  Coverage   97.09%   97.10%           
=======================================
  Files         262      262           
  Lines       17019    17019           
=======================================
+ Hits        16525    16526    +1     
+ Misses        494      493    -1     

Impacted Files	Coverage Δ
geotrek/core/forms.py	94.80% <0.00%> (+1.29%)	⬆️

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