moved this.endBuffering() before this.triggerMethod() (issue 1503)

fixes this bug:
https://github.com/marionettejs/backbone.marionette/issues/1503

P.s. I'm not sure, but buffering for ```this.showEmptyView()``` not so important. Otherwise need to add ```this.endBuffering()``` in both conditions and leave the ```this.startBuffering()``` in the same place

Please comment, thanks.