Fix idxImages initialization

[pierotofy]

Hi 👋

I think there's a problem initializing idxImages in the exportChunks function. Currently the resulting IIndexArr will be initialized to 2*chunk.images.size() size, causing a buffer overflow in SubScene().

There might be a better way to fix this, but this fixes the crash and runs the split functionality as expected.

It's kind of strange because the IIndexArr constructor looks correct on the surface, but:

bool Scene::ExportChunks(const ImagesChunkArr& chunks, const String& path, ARCHIVE_TYPE type) const
{
	FOREACH(chunkID, chunks) {
		const ImagesChunk& chunk = chunks[chunkID];
		std::cerr << "SIZE: " << chunk.images.size() << std::endl;
		IIndexArr idxImages(chunk.images.begin(), chunk.images.end(), true);
		std::cerr << "IDX SIZE: " << idxImages.size() << std::endl;
		exit(1);

SIZE: 66
IDX SIZE: 132

g++ --version
g++ (Ubuntu 9.4.0-1ubuntu1~20.04.2) 9.4.0

[cdcseacave]

thank you @pierotofy for finding this bug, the last commit should fix it