Fix #1288 - error when importing consecutive files.

src/ifcblenderexport/blenderbim/bim/module/document/data.py

@@ -10,6 +10,13 @@ class Data:
     references = {}
     information = {}
 
+    @classmethod
+    def purge(cls):
+        cls.is_loaded = False
+        cls.products = {}
+        cls.references = {}
+        cls.information = {}
+
     @classmethod
     def load(cls, product_id=None):
         cls._file = IfcStore.get_file()