ARLINGTON — Jonah Heim has been one of the best catchers in the American League this season, so it’s almost no surprise that even when he fails, it works out anyway. In the fourth inning of the Rangers’ game against the Mariners on Saturday afternoon at Globe Life Field, Seattle had runners on the corners with two outs after knocking out Texas starter Andrew Heaney earlier in the inning. After Mariners outfielder Julio Rodríguez took off from first base, Heim attempted to catch him stealing — but then appeared to think better of it with José Caballero looming at third.…