(Undated)  --  The XFL is issuing an apology for an officiating error that denied the Dragons the opportunity to tie the Houston Roughnecks at the end of their game on Saturday.  Houston quarterback PJ walker took a knee on fourth down to end the game, but the league said his knee touched the 22-yard line with two seconds remaining.  Seattle should've been given the ball on the 22 with two seconds remaining.  Had they scored, they could've gone for a three-point conversion attempt from the 10 yard line with a chance to tie the game.  "With a nine-point differential in the score, Seattle was denied an opportunity to tie the game," the XFL said in a statement. "The XFL sincerely regrets this error."