draw: Fix memory leak.

This would only be hit if we got and invalid index_size.

src/gallium/auxiliary/draw/draw_pt_vcache.c

@@ -394,6 +394,7 @@ vcache_check_run( struct draw_pt_front_end *frontend,
 
          default:
             assert(0);
+            FREE(storage);
             return;
          }
       }
@@ -422,6 +423,7 @@ vcache_check_run( struct draw_pt_front_end *frontend,
 
          default:
             assert(0);
+            FREE(storage);
             return;
          }
       }