Eric, comments?

TestMipMaps() function in src/OGLconform/textureNPOT.c calls glTexImage2D() with width = 0 and height = 24. Zero image width results in to miptree not allocated for the image. This is due to a condition in function _mesa_store_teximage3d(), src/mesa/main/texstore.c

   if (width == 0 || height == 0 || depth == 0)
      return;

   /* allocate storage for texture data */
   if (!ctx->Driver.AllocTextureImageBuffer(ctx, texImage, texImage->TexFormat,
                                            width, height, depth)) {
      _mesa_error(ctx, GL_OUT_OF_MEMORY, "glTexImage3D");
      return;
   }

   store_texsubimage(ctx, texImage,
                     0, 0, 0, width, height, depth,
                     format, type, pixels, packing, "glTexImage3D");

Removing the following statements from _mesa_store_teximage3d function resolve the issue:
   if (width == 0 || height == 0 || depth == 0)
      return;

But i'm not sure if this breaks any other test. I'll send out a patch for review on mesa mailing list.

This issue has been resolved by below listed patch:
http://www.mail-archive.com/mesa-dev@lists.freedesktop.org/msg17302.html

commit logs on mesa master:
commit f1a9a9bcd19dcbb8a0a4bd7299400cb418970f99
Author: Anuj Phogat <anuj.phogat@gmail.com>
Date:   Mon Jan 16 16:15:30 2012 -0800

    mesa: Add condition in glGetTexImage for zero size textures
    
    TestMipMaps() function in src/OGLconform/textureNPOT.c calls glTexImage2D()
    with width = 0. Texture with zero size skips miptree allocation due to a
    condition in function _mesa_store_teximage3d(). While calling glGetTexImage()
    it results in assertion failure in intel_map_texture_image() due to null mt
    pointer.
    
    This patch fixes the issue by detecting the zero size texture early in
    glGetTexImage and glGetCompressedTexImage functions. In such a case function
    simply returns doing nothing.
    Verified that below mentioned bug is fixed by this patch.
    
    https://bugs.freedesktop.org/show_bug.cgi?id=42334
    
    NOTE: This is a candidate for stable branches
    
    Signed-off-by: Anuj Phogat <anuj.phogat@gmail.com>
    Reviewed-by: Brian Paul <brianp@vmware.com>

I see the patch has landed in mesa 8.0 and 7.11 branch. 

Xun, please verify.

Verified with mesa master branch(aed51e3e) and mesa 8.0 branch(65b50085).