[PATCH libXt] fix NULL check

[Alan Coopersmith]

walter harms wrote:
> _XtGetPerWidgetInput may return NULL
> avoid possible NULL references
> 
>  Signed-off-by: walter harms <wharms at bfs.de>

Fixed indentation to match the surrounding code and pushed to
git master.

-- 
	-Alan Coopersmith-        alan.coopersmith at oracle.com
	 Oracle Solaris Platform Engineering: X Window System