When trace mode is selected and the only active
equation is cleared, a box entitled "Equation Error"
with the text
ERROR: Please enter an equation first
appears. When the OK button is clicked, the box pops
up again. This repeats until the cursor is moved off
the graph window and trace is disabled. Reccommended
fix: automatically disable trace if this error occurs.
This will alleviate frustration of the end user
because the box will only pop up once.