surface.patch

diff --git a/invesalius/data/surface.py b/invesalius/data/surface.py
index 8845085..79ba515 100644
--- a/invesalius/data/surface.py
+++ b/invesalius/data/surface.py
@@ -774,16 +774,16 @@ class SurfaceManager():
         session = ses.Session()
         session.ChangeProject()
 
-        # The following lines have to be here, otherwise all volumes disappear
-        measured_polydata = vtk.vtkMassProperties()
-        #  measured_polydata.ReleaseDataFlagOn()
-        measured_polydata.SetInputData(to_measure)
-        volume =  float(measured_polydata.GetVolume())
-        area =  float(measured_polydata.GetSurfaceArea())
-        surface.volume = volume
-        surface.area = area
-        self.last_surface_index = surface.index
-        del measured_polydata
+        if wx.GetApp() is not None:
+            measured_polydata = vtk.vtkMassProperties()
+            #  measured_polydata.ReleaseDataFlagOn()
+            measured_polydata.SetInputData(to_measure)
+            volume =  float(measured_polydata.GetVolume())
+            area =  float(measured_polydata.GetSurfaceArea())
+            surface.volume = volume
+            surface.area = area
+            self.last_surface_index = surface.index
+            del measured_polydata
         del to_measure
 
         Publisher.sendMessage('Load surface actor into viewer', actor)