ralloc: don't write to memory in case of alloc fail.

For some reason I made this happen under indirect rendering,
I think we might have a leak, valgrind gave out, so I said I'd
fix the basic problem.

NOTE: This is a candidate for stable branches.
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Signed-off-by: Dave Airlie <airlied@redhat.com>
(cherry picked from commit 47bd6e46fe)

src/glsl/ralloc.c

@@ -108,6 +108,8 @@ ralloc_size(const void *ctx, size_t size)
 {
    void *block = calloc(1, size + sizeof(ralloc_header));
 
+   if (unlikely(block == NULL))
+      return NULL;
    ralloc_header *info = (ralloc_header *) block;
    ralloc_header *parent = ctx != NULL ? get_header(ctx) : NULL;