From b36564f638d28e6a0d9460cad13357948856d39d Mon Sep 17 00:00:00 2001
From: Bertrand Bordage <bordage.bertrand@gmail.com>
Date: Wed, 27 Feb 2019 00:08:30 +0100
Subject: [PATCH] Fixes an error occurring when a validation error occurs
 nested in a ListBlock.

---
 wagtail/core/blocks/utils.py | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/wagtail/core/blocks/utils.py b/wagtail/core/blocks/utils.py
index 7cd72267370..d042dde8c7a 100644
--- a/wagtail/core/blocks/utils.py
+++ b/wagtail/core/blocks/utils.py
@@ -35,7 +35,9 @@ def get_non_block_errors(errors):
         errors_data = errors_data[0].params
         if errors_data is None:
             return errors
-    return errors_data.get(NON_FIELD_ERRORS, ())
+    if isinstance(errors_data, dict):
+        return errors_data.get(NON_FIELD_ERRORS, ())
+    return ()
 
 
 class BlockData: