- When an embedded texture is empty, skip it instead of trying to copy it. This must fail.
- closes https://github.com/assimp/assimp/issues/4238
- Found from the Google fuzzer.
Some allocations might underallocate due to integer overflows. This
commit ensures that we are throwing an exception if the allocation size
does not fit in an unsigned int.
Fix https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=25341
