Ultraliser::Mesh segfaults on destructor

[NadirRoGue]

Ultraliser::Mesh objects built from Ultraliser::NeuronMorphology objects produce a double free on the following line:

Ultraliser/ultraliser/data/meshes/simple/MeshOptimization.cpp

Line 91 in 22128ba

delete firstNGR;

It can be tested by adding delete mesh; after this:

Ultraliser/ultraliser/data/volumes/Volume.cpp

Lines 510 to 511 in 22128ba

	auto mesh = new Mesh(neuronMorphology);
	_rasterize(mesh, _grid);

(The fact the mesh isnt being released is already a memory leak. There are futher memory leaks on the same function where this line belongs to).