Compilation warnings

[szymonlopaciuk]

I have decided to tackle some compilation warnings throughout Xsuite, and the following come from Xcoll (summary):

EverestCollimator_track_local_particle
- ‘coll’ may be used uninitialized [-Wmaybe-uninitialized]
- ‘cg’ may be used uninitialized [-Wmaybe-uninitialized]
- ‘material’ may be used uninitialized [-Wmaybe-uninitialized]

EverestCrystal_track_local_particle
- ‘coll’ may be used uninitialized [-Wmaybe-uninitialized]
- ‘cg’ may be used uninitialized [-Wmaybe-uninitialized]
- ‘material’ may be used uninitialized [-Wmaybe-uninitialized]