HOUSTON — Without Cal Raleigh, Mitch Garver wouldn’t be here. He wouldn’t have a spot on the Mariners roster and wouldn’t have a chance to hold down the catching position during Raleigh’s sudden absence.  In the short term, at least, Garver showed Thursday that the Mariners just might be OK without their star catcher. A few hours after Raleigh landed on the injured list for the first time in his career, Garver hit his first home run of the season to help lift the Mariners to an 8-3 victory over the Astros and close out a winning road trip. “First and foremost, we just want (Raleigh) to get healthy,” Garver said postgame. “It’s not fun being hurt. I know he doesn’t really have experience with that, so we’re going to be there for him, support him in that aspect. But the show must go on.…