Unit test EMA model

* adds unit test for EMA model

ema/models/ema.py

@@ -122,7 +122,7 @@ class EmaDocument(AbstractDocument):
 
     def delete(self, user=None, *args, **kwargs):
         """
-        Custom delete functionality for EcoAccountDocuments.
+        Custom delete functionality for EmaDocuments.
         Removes the folder from the file system if there are no further documents for this entry.
 
         Args:
@@ -139,8 +139,11 @@ class EmaDocument(AbstractDocument):
             # The only file left for this EMA is the one which is currently processed and will be deleted
             # Make sure that the compensation folder itself is deleted as well, not only the file
             # Therefore take the folder path from the file path
-            folder_path = self.file.path.split("/")[:-1]
-            folder_path = "/".join(folder_path)
+            try:
+                folder_path = self.file.path.split("/")[:-1]
+                folder_path = "/".join(folder_path)
+            except ValueError:
+                folder_path = None
 
         if user:
             self.instance.mark_as_edited(user, edit_comment=DOCUMENT_REMOVED_TEMPLATE.format(self.title))