Update the model to remove the required formatting from the admin

opentech/public/projects/migrations/0004_projectpage_categories.py

@@ -15,6 +15,6 @@ class Migration(migrations.Migration):
         migrations.AddField(
             model_name='projectpage',
             name='categories',
-            field=models.TextField(default='{}'),
+            field=models.TextField(default='{}', blank=True),
         ),
     ]

opentech/public/projects/models.py

@@ -109,7 +109,7 @@ class ProjectPage(FundingMixin, BasePage):
     status = models.CharField(choices=STATUSES, max_length=25, default=STATUSES[0][0])
     body = StreamField(StoryBlock())
 
-    categories = models.TextField(default="{}")
+    categories = models.TextField(default='{}', blank=True)
 
     search_fields = BasePage.search_fields + [
         index.SearchField('introduction'),