fixing free

git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@707 c046a42c-6fe2-441c-8c8c-71466251a162

osdep.c

@@ -235,6 +235,8 @@ void qemu_free(void *ptr)
 {
     MemoryBlock *mb;
 
+    if (!ptr)
+        return;
     mb = (MemoryBlock *)((uint8_t *)ptr - BLOCK_HEADER_SIZE);
     mb->next = first_free_block;
     first_free_block = mb;