FIX (#2053): materialeditor (qt3) gives vtk errors and crashes upon close
FIX (#2053): materialeditor (qt3) gives vtk errors and crashes upon close

added necessary delete of qmitkrenderwindow in QmitkMaterialShowcase::destroy()


iwegner/MITK,NifTK/MITK,lsanzdiaz/MITK-BiiG,fmilano/mitk,NifTK/MITK,nocnokneo/MITK,RabadanLab/MITKats,MITK/MITK,fmilano/mitk,nocnokneo/MITK,nocnokneo/MITK,MITK/MITK,lsanzdiaz/MITK-BiiG,fmilano/mitk,rfloca/MITK,rfloca/MITK,rfloca/MITK,NifTK/MITK,nocnokneo/MITK,rfloca/MITK,RabadanLab/MITKats,danielknorr/MITK,iwegner/MITK,NifTK/MITK,MITK/MITK,iwegner/MITK,lsanzdiaz/MITK-BiiG,rfloca/MITK,lsanzdiaz/MITK-BiiG,danielknorr/MITK,MITK/MITK,fmilano/mitk,RabadanLab/MITKats,lsanzdiaz/MITK-BiiG,nocnokneo/MITK,rfloca/MITK,nocnokneo/MITK,MITK/MITK,RabadanLab/MITKats,MITK/MITK,iwegner/MITK,lsanzdiaz/MITK-BiiG,iwegner/MITK,RabadanLab/MITKats,danielknorr/MITK,danielknorr/MITK,danielknorr/MITK,danielknorr/MITK,fmilano/mitk,iwegner/MITK,danielknorr/MITK,nocnokneo/MITK,RabadanLab/MITKats,lsanzdiaz/MITK-BiiG,fmilano/mitk,fmilano/mitk,NifTK/MITK,rfloca/MITK,NifTK/MITK,lsanzdiaz/MITK-BiiG