St Johnstone goalkeeper Joshua Rae might well have taken Rangers winger Ross McCausland off his Christmas card list this afternoon in Glasgow. The young Northern Irishman didn’t start the Premier Sports Cup clash between Rangers and the Perthshire Saints at Hampden, but boy did he finish it. In a potential banana skin for the Rangers team, Ross McCausland popped up with a crucial second goal for the club just moments after St Johnstone had blown a huge chance to equalise. Softly dinking the ball over the outrushing Joshua Rae when it broke to him in the box, it was a composed finish in the sty…