Fix zero division bugs in frame

src/primitives/frame.coffee

@@ -29,14 +29,18 @@ class Frame extends EventEmitter
	@define "midX",
		get: -> @x + (@width / 2.0)
		set: (value) ->
			throw Error "Width is zero" if @width is 0
			@x = value - (@width / 2.0)
			if @width is 0
				@x = 0
			else
				@x = value - (@width / 2.0)

	@define "maxX",
		get: -> @x + @width
		set: (value) ->
			throw Error "Width is zero" if @width is 0
			@x = value - @width
			if @width is 0
				@x = 0
			else
				@x = value - @width

	@define "minY",
		get: -> @y
@@ -45,14 +49,20 @@ class Frame extends EventEmitter
	@define "midY",
		get: -> @y + (@height / 2.0)
		set: (value) ->
			throw Error "Width is zero" if @height is 0
			@y = value - (@height / 2.0)
			if @height is 0
				@y = 0
			else
				@y = value - (@height / 2.0)



	@define "maxY",
		get: -> @y + @height
		set: (value) ->
			throw Error "Width is zero" if @height is 0
			@y = value - @height
			if @height is 0
				@y = 0
			else
				@y = value - @height

	merge: (r2) ->
		r1 = @