It happens on very small screen ( < 400px height), as in the case of virtual machines, or adding additional children to Main.overview._overview even on normal resolution (768px height)

In appDisplay.js, Allview.adaptToSize

...

 let fadeOffset = Math.min(this._grid.topPadding,
                                  this._grid.bottomPadding);
 this._scrollView.update_fade_effect(fadeOffset, 0);
 this._scrollView.get_effect('fade').fade_edges = true;

...

fadeOffset is calculated from the _grid  paddings which turn out to be zero on the conditions mentioned above. In these conditions the fade effect is disabled by update_fade_effect(0, 0) and the following line and others result in an error.

The bug also affects 3.14.