Crash when loading hdr lightmaps

[AntiAnti]

It's quite weird. I get this crash when loading my baked lighting on laptop. It doesn't happen on desktop PC (why??) and doesn't happen on laptop with lighting baked by SomaZ (for t1_rail). The crash happens when it tries to load non-existing sky texture, but I didn't dig deeper. Anyway, solution is quite simple.

R_FindImageFile function in tr_image.cpp tries to load HDR image and then checks if it succeed by testing output buffer:

		R_LoadHDRImage(filename, &pic, &width, &height);
		if (pic == NULL)
			...

The problem is, R_LoadHDRImage doesn't reset buffer to NULL if it failed.
So, in shared/rd-rend2/tr_image_stb.cpp need to add three lines:

// Loads a HDR image from file.
void R_LoadHDRImage( const char *filename, byte **data, int *width, int *height )
{
	byte *buf = NULL;
	int x, y, n;

	int len = ri.FS_ReadFile (filename, (void **)&buf);
	if ( len <= 0 || buf == NULL )
	{
		// reset output varialbes
		*data = NULL;
		*width = 0;
		*height = 0;

		return;
	}
	...

[SomaZ]

Meh, forgot to co-author you. Sorry about that. Hope that's ok.