Fixes DockArea save/restore  when topContainer is None (i.e. when no docks are present, or when all are in temporary windows).
Fixes DockArea save/restore  when topContainer is None (i.e. when no docks are present, or when all are in temporary windows).

campagnola/acq4,acq4/acq4,ddamiani/pyqtgraph,mgraupe/acq4,ng110/pyqtgraph,petebachant/pyqtgraph,acq4/acq4,JenSte/pyqtgraph,carlomt/dicom_tools,pbmanis/acq4,mgraupe/acq4,JenSte/pyqtgraph,welshjf/pyqtgraph,tropp/acq4,onlyjus/pyqtgraph,stscieisenhamer/pyqtgraph,benvermaercke/pyqtgraph,campagnola/acq4,jlombacher/pyqtgraph,gvalentine/pyqtgraph,mgraupe/acq4,duguxy/pyqtgraph,carlomt/dicom_tools,petebachant/pyqtgraph,tropp/acq4,meganbkratz/acq4,nmearl/pyqtgraph,onlyjus/pyqtgraph,pbmanis/acq4,pbmanis/acq4,mgraupe/acq4,derricw/pyqtgraph,meganbkratz/acq4,onlyjus/pyqtgraph,ddamiani/pyqtgraph,welshjf/pyqtgraph,duguxy/pyqtgraph,mpvismer/pyqtgraph,benvermaercke/pyqtgraph,tropp/acq4,campagnola/acq4,meganbkratz/acq4,welshjf/pyqtgraph,ericdill/pyqtgraph,jlombacher/pyqtgraph,gvalentine/pyqtgraph,pmaunz/pyqtgraph,mgraupe/acq4,gvalentine/pyqtgraph,ericdill/pyqtgraph,derricw/pyqtgraph,ddamiani/pyqtgraph,meganbkratz/acq4,nmearl/pyqtgraph,benvermaercke/pyqtgraph,ng110/pyqtgraph,pbmanis/acq4,campagnola/acq4,acq4/acq4,stscieisenhamer/pyqtgraph,tropp/acq4,pmaunz/pyqtgraph,mpvismer/pyqtgraph,ericdill/pyqtgraph,acq4/acq4