Mikel Arteta was left with his head in his hands after what Gabriel Martinelli did during the first-half as Arsenal took on Bayern Munich on Wednesday. Arsenal could definitely be happy with their first-half performance in the Allianz Arena. Of course, Mikel Arteta‘s men had a real point to prove after a difficult week, which included a 2-2 draw with Thomas Tuchel’s side in the first-leg. It was a tense 45 minutes, lacking in any real quality when it really mattered. There were a couple of nervy moments for the Premier League title contenders. But Arsenal also gave a good account of themselves…