QT: Fixed a segmentation fault that only occured if you auto-scrolled in one direction for a very long time, it eventually messed up the stack.

Instead of calling ctx->redraw() to redraw the window, call ctx->set_dirty().
The GlowCtx will redraw the window at the end of the event_handler if any event has marked it as dirty.
If you really need to redraw the window NOW (ex. after a timer triggered event),
call ctx->set_dirty followed by ctx->redraw_if_dirty().

Instead of calling ctx->redraw() to redraw the window, call ctx->set_dirty().
The FlowCtx will redraw the window at the end of the event_handler if any event has marked it as dirty.
If you really need to redraw the window NOW (ex. after a timer triggered event),
call ctx->set_dirty followed by ctx->redraw_if_dirty().