Fix ever-increasing `_nextFrame` value on MovieClip instances with one frame
Fix ever-increasing `_nextFrame` value on MovieClip instances with one frame

I guess they shouldn't ever even be calling advanceFrame, but I had an intermittendly-occurring case of this, and the check isn't incorrect in and of itself.

tschneidereit/shumway,tschneidereit/shumway,tschneidereit/shumway,mozilla/shumway,mozilla/shumway,mbebenita/shumway,mbebenita/shumway,tschneidereit/shumway,tschneidereit/shumway,tschneidereit/shumway,mbebenita/shumway,mbebenita/shumway,yurydelendik/shumway,mozilla/shumway,mbebenita/shumway,mozilla/shumway,yurydelendik/shumway,mbebenita/shumway,tschneidereit/shumway,mbebenita/shumway,mozilla/shumway,yurydelendik/shumway,tschneidereit/shumway,mbebenita/shumway,yurydelendik/shumway,yurydelendik/shumway,mozilla/shumway,mozilla/shumway,yurydelendik/shumway,yurydelendik/shumway,mozilla/shumway,yurydelendik/shumway