[PATCH] uml: avoid NULL dereference in line.c

This patch reorders two lines to check a variable for NULL before using 
the variable.
Signed-off-by: Frank Sorenson <frank@tuxrocks.com>
Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade_spam@yahoo.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/um/drivers/line.c

@@ -593,8 +593,8 @@ irqreturn_t winch_interrupt(int irq, void *data, struct pt_regs *unused)
 		}
 	}
 	tty  = winch->tty;
-	line = tty->driver_data;
 	if (tty != NULL) {
+		line = tty->driver_data;
 		chan_window_size(&line->chan_list,
 				 &tty->winsize.ws_row, 
 				 &tty->winsize.ws_col);