mesa/objectlabel: don't do memcpy if bufSize is 0 (v2)

This prevents GL43-CTS.khr_debug.labels_non_debug from
memcpying all over the stack and crashing.

v2: actually fix the test.

Reviewed-by: Alejandro Piñeiro <apinheiro@igalia.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

src/mesa/main/objectlabel.c

@@ -104,6 +104,11 @@ copy_label(const GLchar *src, GLchar *dst, GLsizei *length, GLsizei bufSize)
     * will be returned in <length>."
     */
 
+   if (bufSize == 0) {
+      if (length)
+         *length = strlen(src);
+      return;
+   }
    if (src)
       labelLen = strlen(src);