fix null ref when presenter switches before video control buttons load fully
Reworked the zoom calculation and fixed it, but I think it can be improved more
forgot to put in bounds checks after a zoom, specifically zoom out
fixed a different presentation edge case bug that I just discovered
Merge pull request #93 from SenecaCDOT-BigBlueButton/fix-presentation-zoom

Fix presentation zoom
Merge pull request #85 from SenecaCDOT-BigBlueButton/fix-controlbutton-null-ref

fix null ref when presenter switches before video control buttons load fully
Merge remote-tracking branch 'upstream/master'