shell/panelview: Use the panel geometry as a fallback for the mask
It seems like in some scenarios (e.g. detaching and reattaching monitors) ksvg provides an empty mask until the panel is re-drawn; as a first workaround, we add a fallback that avoids the panel spilling into other monitors when an empty mask is provided.
BUG: 481380 FIXED-IN: 6.1
Edited by Nate Graham