- MainWindowLayoutInfo: toXml() iterated open_sequences_ for the
<viewers> section and fromXml() never parsed it, so open footage
viewers were lost on layout save/load
- PanelWidget never set QObject::objectName, so
PanelManager::GetPanelWithName() always returned nullptr and every
caller (layout restore, NodeView param panel lookup) was dead code
- PanelManager::DestroyInstance() left instance_ dangling (UAF on any
later RegisterPanel), unlike the other singletons
Mike-Solar
c812f6ea28