Fixed "invalid drawable" message in log
Fixed "invalid drawable" message in log

gui/mashups/mashup_app.py:
- initCells:
  Assign cell to widget before updating contents

VisTrails/VisTrails,Nikea/VisTrails,hjanime/VisTrails,Nikea/VisTrails,VisTrails/VisTrails,hjanime/VisTrails,celiafish/VisTrails,VisTrails/VisTrails,Nikea/VisTrails,VisTrails/VisTrails,minesense/VisTrails,hjanime/VisTrails,minesense/VisTrails,minesense/VisTrails,celiafish/VisTrails,hjanime/VisTrails,Nikea/VisTrails,celiafish/VisTrails,minesense/VisTrails,VisTrails/VisTrails,hjanime/VisTrails,minesense/VisTrails,celiafish/VisTrails