[Fix] Iuclid export produce only one root substance (#429)

Reviewed-on: enviPath/enviPy#429
Co-authored-by: Tobias O <tobias.olenyi@envipath.com>
Co-committed-by: Tobias O <tobias.olenyi@envipath.com>

epiuclid/tests/test_api.py

@@ -70,8 +70,7 @@ class IUCLIDExportAPITest(TestCase):
             names = zf.namelist()
             self.assertIn("manifest.xml", names)
             i6d_files = [n for n in names if n.endswith(".i6d")]
-            # 2 substances + 2 ref substances + 1 ESR = 5 i6d files
-            self.assertEqual(len(i6d_files), 5)
+            self.assertEqual(len(i6d_files), 4)
 
     def test_anonymous_returns_401(self):
         self.client.logout()