solove two bugs and color restriction update

Bug1:
In solving scene, if choice panel is open and continuously click other
areas to close it, after this point the input will be invalided.
Bug2:
In teching scene, at the begining, if you choose 'continue' the program
will break down.
Color restriction:
If the face is filled with some color and you click it again, now you
can choose any color without any restriction.