Fixed possible crash when empty model id is passed

flask_admin/model/base.py

@@ -1543,7 +1543,8 @@ class BaseModelView(BaseView, ActionsMixin):
         form = self.delete_form()
 
         if self.validate_form(form):
-            id = form.id.data # id is Required()
+             # id is Required()
+            id = form.id.data
 
             model = self.get_one(id)
 

flask_admin/model/helpers.py

@@ -25,7 +25,13 @@ def get_mdict_item_or_list(mdict, key):
     if hasattr(mdict, 'getlist'):
         v = mdict.getlist(key)
         if len(v) == 1:
-            return v[0]
+            value = v[0]
+
+            # Special case for empty strings, treat them as "no-value"
+            if value == '':
+                value = None
+
+            return value
         elif len(v) == 0:
             return None
         else: