Switch to log scale raises exception *after* editing figure options. #7098

2.0b4.

plot([0, 1, 2])

Pressing l (switch y to log-scale) results in ignoring the point at (0, 0) for the autoscaling which is a fairly reasonable thing to do. But after opening the figure options, not editing anything and pressing OK, pressing l now results in a crash during the figure redraw (basically because the ylims are now considered to be force-set).
Note that #6983 cannot handle this because the key handler only calls draw_idle, so the exception occurs too late to be caught.