variables: don't treat invalid json as formatted values (#26703)

hobo/environment/models.py

@@ -39,7 +39,10 @@ class Variable(models.Model):
     @property
     def json(self):
         if self.value and (self.value[0] in '{[' or self.value in ('true', 'false')):
-            return json.loads(self.value)
+            try:
+                return json.loads(self.value)
+            except ValueError:
+                pass
         return self.value
 
     def clean(self):