[2.0.x] Fixed #29273 -- Prevented initial selection of empty choice in multiple choice widgets.

Regression in b52c73008a9d67e9ddbb841872dc15cdd3d6ee01.

Backport of f3b69f9757ec03057441ebbd52b7cdbfed31fb32 from master.

1 files changed, 2 insertions, 0 deletions

diff --git a/django/forms/widgets.py b/django/forms/widgets.py
index 47396213d9..976487cb23 100644
--- a/django/forms/widgets.py
+++ b/django/forms/widgets.py
@@ -658,6 +658,8 @@ class ChoiceWidget(Widget):
 
     def format_value(self, value):
         """Return selected values as a list."""
+        if value is None and self.allow_multiple_selected:
+            return []
         if not isinstance(value, (tuple, list)):
             value = [value]
         return [str(v) if v is not None else '' for v in value]