Ensure null values cannot be picked which result in bad IFC data

src/ifcblenderexport/io_export_ifc/prop.py

@@ -33,7 +33,6 @@ documents_enum = []
 def getIfcPredefinedTypes(self, context):
     global types_enum
     if len(types_enum) < 1:
-        types_enum.append((' ', 'None',''))
         for name, data in ifc_schema.elements.items():
             if name != self.ifc_class.strip():
                 continue
@@ -48,14 +47,11 @@ def refreshPredefinedTypes(self, context):
     global types_enum
     types_enum.clear()
     getIfcPredefinedTypes(self, context)
-    # set to None
-    self.ifc_predefined_type = " "
 
 
 def getIfcClasses(self, context):
     global classes_enum
     if len(classes_enum) < 1:
-        classes_enum.append((' ', 'None', ''))
         classes_enum.extend([(e, e, '') for e in ifc_schema.elements])
     return classes_enum
 
@@ -64,7 +60,6 @@ def getPsetNames(self, context):
     global psetnames_enum
     if len(psetnames_enum) < 1:
         psetnames_enum.clear()
-        psetnames_enum.append((' ', 'None', ''))
         files = os.listdir(os.path.join(self.data_dir, 'pset'))
         psetnames_enum.extend([(f, f, '') for f in files])
     return psetnames_enum
@@ -73,13 +68,10 @@ def refreshPsetFiles(self, context):
     global psetfiles_enum
     psetfiles_enum.clear()
     getPsetFiles(self, context)
-    # set to None
-    self.pset_file = " "
 
 def getPsetFiles(self, context):
     global psetfiles_enum
     if len(psetfiles_enum) < 1:
-        psetfiles_enum.append((' ', 'None', ''))
         if not self.pset_name.strip():
             return psetfiles_enum
         files = os.listdir(os.path.join(self.data_dir, 'pset', self.pset_name.strip()))
@@ -90,7 +82,6 @@ def getClassifications(self, context):
     global classification_enum
     if len(classification_enum) < 1:
         classification_enum.clear()
-        classification_enum.append((' ', 'None', ''))
         with open(os.path.join(self.data_dir, 'class', 'classifications.csv'), 'r') as f:
             data = list(csv.reader(f))
             keys = data.pop(0)
@@ -102,13 +93,10 @@ def refreshReferences(self, context):
     global reference_enum
     reference_enum.clear()
     getReferences(self, context)
-    # set to None
-    self.reference = " "
 
 def getReferences(self, context):
     global reference_enum
     if len(reference_enum) < 1:
-        reference_enum.append((' ', 'None', ''))
         if not self.classification.strip():
             return reference_enum
         with open(os.path.join(self.data_dir, 'class', 'references.csv'), 'r') as f:
@@ -121,7 +109,6 @@ def getReferences(self, context):
 def getApplicableAttributes(self, context):
     global attributes_enum
     attributes_enum.clear()
-    attributes_enum.append((' ', 'None', ''))
     if '/' in context.active_object.name \
         and context.active_object.name.split('/')[0] in ifc_schema.elements:
         attributes_enum.extend([(a['name'], a['name'], '') for a in
@@ -132,7 +119,6 @@ def getApplicableAttributes(self, context):
 def getApplicableDocuments(self, context):
     global documents_enum
     documents_enum.clear()
-    documents_enum.append((' ', 'None', ''))
     doc_path = os.path.join(context.scene.BIMProperties.data_dir, 'doc')
     for filename in Path(doc_path).glob('**/*'):
         uri = str(filename.relative_to(doc_path).as_posix())