[OpenGEX] Crash when attempt load bundled test OpenGEX 3D model files

[tellypresence]

Getting crashes when attempting to load bundled OpenGEX models. Reason appears to be that when iterating in OpenGEXImporter::resolveReferences(), this line is failing:

    node->mMeshes[i] = meshIdx;

because i greater than or equal to value of node->mNumMeshes.

Can easily observe this problem by adding logging around that line in OpenGEXImporter::resolveReferences() e.g.

    if (i < node->mNumMeshes) {
        node->mMeshes[i] = meshIdx;
        // Log success...
    } else {
        // Log failure...
    }

Affected models:

Model
test/models/OpenGEX/animation_example.ogex
test/models/OpenGEX/camera.ogex
test/models/OpenGEX/collada.ogex

[tellypresence]

Note that many errors were "masked" due to early non-catastrophic termination during load due to other factors

Assimp commit	Model	Error
12 Jun 2019 a4907e5	test/models/OpenGEX/animation_example.ogex	OpenGEX: Not enough values to fill 4-element color, only 3
	test/models/OpenGEX/camera.ogex	Validation failed: The mesh contains no vertices
	test/models/OpenGEX/collada.ogex	Validation failed: aiScene::mLights[3] has no corresponding node in the scene graph (light3)
15 Nov 2017 98da53e	test/models/OpenGEX/animation_example.ogex	Crash on attempt load
	test/models/OpenGEX/camera.ogex	aiScene::mLights[1] has no corresponding node in the scene graph (light1)
	test/models/OpenGEX/collada.ogex	Validation failed: aiScene::mLights[3] has no corresponding node in the scene graph (light3)

[tellypresence]

Please add "OpenGEX" label to this issue