added a null arg to getComputedStyle, to placate FF3.6
added a null arg to getComputedStyle, to placate FF3.6

jeresig/processing-js,baiyanghese/processing-js,kevinb7/processing-js,jaredly/processing-js,jaredly/processing-js,baiyanghese/processing-js,guazipi/processing-js,kevinb7/processing-js,guazipi/processing-js,jeresig/processing-js