[FIX] gamification: prevent traceback in goals history

Closes #1536

addons/gamification/models/challenge.py

@@ -852,7 +852,7 @@ class gamification_challenge_line(osv.Model):
         return ret
 
     _columns = {
-        'name': fields.related('definition_id', 'name', string="Name"),
+        'name': fields.related('definition_id', 'name', string="Name", type="char"),
         'challenge_id': fields.many2one('gamification.challenge',
             string='Challenge',
             required=True,

addons/gamification/views/goal.xml

@@ -23,7 +23,7 @@
             <field name="name">Goal List</field>
             <field name="model">gamification.goal</field>
             <field name="arch" type="xml">
-                <tree string="Goal List" colors="red:state == 'failed';green:state == 'reached';grey:state == 'canceled'"> 
+                <tree string="Goal List" colors="red:state == 'failed';green:state == 'reached';grey:state == 'canceled'" create="false">
                     <field name="definition_id" invisible="1" />
                     <field name="user_id" invisible="1" />
                     <field name="start_date"/>