Assimp checks against lowercase extensions, so we force the extension of the file to lower before fetching the importer. Also adds sanity check that the importer was actually found before we try and use it.
Assimp checks against lowercase extensions, so we force the extension of the file to lower before fetching the importer.
Also adds sanity check that the importer was actually found before we try and use it.

chaigler/Torque3D,chaigler/Torque3D,Bloodknight/Torque3D,chaigler/Torque3D,Bloodknight/Torque3D,chaigler/Torque3D,chaigler/Torque3D,chaigler/Torque3D,Bloodknight/Torque3D,chaigler/Torque3D,Bloodknight/Torque3D,Bloodknight/Torque3D,Bloodknight/Torque3D,chaigler/Torque3D,Bloodknight/Torque3D,Bloodknight/Torque3D,Bloodknight/Torque3D,chaigler/Torque3D