Catch erros and open the write stream only if the material cointaner is found

CURA-5555

plugins/UFPWriter/UFPWriter.py

@@ -24,6 +24,8 @@ class UFPWriter(MeshWriter):
         self._snapshot = None
         Application.getInstance().getOutputDeviceManager().writeStarted.connect(self._createSnapshot)
 
+        self._default_data_path ="/Cura/"
+
     def _createSnapshot(self, *args):
         # must be called from the main thread because of OpenGL
         Logger.log("d", "Creating thumbnail image...")
@@ -66,19 +68,24 @@ class UFPWriter(MeshWriter):
         global_stack = machine_manager.activeMachine
         container_registry = application.getContainerRegistry()
 
-        archive.addContentType(extension="xml.fdm_material", mime_type="application/x-ultimaker-material-profile")
+        material_extension = "xml.fdm_material"
+        material_mime_type = "application/x-ultimaker-material-profile"
+
+        try:
+            archive.addContentType(extension=material_extension, mime_type=material_mime_type)
+        except:
+            Logger.log("w", "The material extension: %s was already added", material_extension)
 
         added_materials = []
         for extruder_stack in global_stack.extruders.values():
             material = extruder_stack.material
             material_file_name = material.getMetaData()["base_file"] + ".xml.fdm_material"
-            material_file_name = "/Cura/" + material_file_name
+            material_file_name = self._default_data_path + material_file_name
 
             #Same material cannot be added
             if material_file_name in added_materials:
                 continue
 
-            material_file = archive.getStream(material_file_name)
             material_containers = container_registry.findContainers(id=material.getMetaDataEntry("base_file"))
 
             if not material_containers:
@@ -92,10 +99,10 @@ class UFPWriter(MeshWriter):
                 Logger.log("e", "Unable serialize material container with id: %s", material.id)
                 return False
 
+            material_file = archive.getStream(material_file_name)
             material_file.write(serialized_material.encode("UTF-8"))
             archive.addRelation(virtual_path=material_file_name,relation_type="http://schemas.ultimaker.org/package/2018/relationships/xml.fdm_material")
 
-
             added_materials.append(material_file_name)
 
         archive.close()