For cards that have optional targets (i.e. Demon Wrangler) I have too many times found myself clicking right next to the target I intended and instead canceling the action. There should be a explicit no-target option to click somewhere if you wish to not use the effect.
Yes, i agree. It can be quite frustrating sometimes, especially with a sac Deck and Demon Wrangler. I would suggest to changing it so, that you can only cancel gift effects with rightclicks and not with Leftclicks.