Tab bar cannot be initialized with files due to undefined imageSheet variable

[mdsandell]

You cannot call widget.newTabBar() with image files (not an image sheet), due to initWithImageFiles attempting to use (unnecessarily) an undefined "imageSheet" variable. I'm pretty sure this line can simply be deleted to fix the issue, but I'm not sure how to test this myself.

Example taken from documentation:

-- Create the widget
local tabBar = widget.newTabBar(
    {
        left = 0,
        top = display.contentHeight-120,
        width = 580,
        height = 120,
        backgroundFile = "tabBarBack.png",
        tabSelectedLeftFile = "tabBarSelL.png",
        tabSelectedRightFile = "tabBarSelR.png",
        tabSelectedMiddleFile = "tabBarSelM.png",
        tabSelectedFrameWidth = 40,
        tabSelectedFrameHeight = 120,
        buttons = tabButtons
    }
)

Failure:

Variable 'imageSheet' is not declared

File: /Users/vlad/actions-runner/_work/corona/corona/subrepos/widget/widgetLibrary/widget_tabbar.lua
Line: 227

stack traceback:
	[C]: in function 'error'
	strict.lua:24: in function <strict.lua:22>
	/Users/vlad/actions-runner/_work/corona/corona/subrepos/widget/widgetLibrary/widget_tabbar.lua:227: in function 'initWithImageFiles'
	/Users/vlad/actions-runner/_work/corona/corona/subrepos/widget/widgetLibrary/widget_tabbar.lua:851: in function </Users/vlad/actions-runner/_work/corona/corona/subrepos/widget/widgetLibrary/widget_tabbar.lua:754>
	(tail call): ?
	/Users/vlad/actions-runner/_work/corona/corona/subrepos/widget/widgetLibrary/widget.lua:135: in function </Users/vlad/actions-runner/_work/corona/corona/subrepos/widget/widgetLibrary/widget.lua:122>
	(tail call): ?
	main.lua:841: in function 'createTabBar'
	main.lua:873: in main chunk