Comment 4 for bug 1630796

AFAICT not fixed with lp:inkscape/0.92.x r15096

Steps to reproduce (incl. crash):
1) launch inkscape
2) switch to the Pencil tool
3) activate Simplify LPE on the Pencil tool controls bar
4) draw a path
5) draw another path
6) switch current selected path with <TAB>
7) open Path Effects editor
8) flatten the Simplify effect by clicking on the button in the Pencil tool controls bar
9) click on the Eye icon of the 'Simplify' path effect still listed as active in the Path Effects dialog

--> crash

The crash can also be reproduced with only one path drawn:
1) launch inkscape
2) draw a path with the Pencil tool using 'Simplify' LPE
3) switch to the select tool, de-select and re-select the path just drawn
4) open Path Effects dialog
5) switch to the Pencil tool
6) flatten the Simplify effect by clicking on the button in the Pencil tool controls bar
7) click on the Eye icon of the 'Simplify' path effect still listed as active in the Path Effects dialog

--> crash:

Program received signal EXC_BAD_ACCESS, Could not access memory.
Reason: KERN_INVALID_ADDRESS at address: 0x00000000000000e0
0x0000000100600906 in Inkscape::UI::Dialog::LivePathEffectEditor::on_visibility_toggled ()