GUI: Allow ESC to finish drawing bezier curves instead of deleting them.

With this pressing ESC while drawing a bezier curve finishes it instead of
deleting it. This reverts the behaviour introduced in b34d9a2
(p.r. solvespace#1386). ESC still deletes the last segment of line segments and
cancels arcs and circles.

This makes it easier to draw non closed curves - otherwise the only way
to finish them was with a right-click.

src/graphicswin.cpp

@@ -1106,7 +1106,6 @@ void GraphicsWindow::MenuEdit(Command id) {
             if ( (SS.GW.pending.operation == Pending::DRAGGING_NEW_POINT)
               || (SS.GW.pending.operation == Pending::DRAGGING_NEW_LINE_POINT)
               || (SS.GW.pending.operation == Pending::DRAGGING_NEW_ARC_POINT)
-              || (SS.GW.pending.operation == Pending::DRAGGING_NEW_CUBIC_POINT)
               || (SS.GW.pending.operation == Pending::DRAGGING_NEW_RADIUS) )
             {
               SS.GW.ClearSuper();