[FIX] website_slides: handle invalid youtube URL.

Also update demo data to point to an available youtube video.

addons/website_slides/data/website_slides_demo.xml

@@ -74,8 +74,8 @@
             <field name="tag_ids" eval="[(4, ref('tag1'))]"/>
         </record>
         <record id="slide_5" model="slide.slide">
-            <field name="name">Odoo POS Indiegogo Campaign</field>
-            <field name="url">https://www.youtube.com/watch?v=C_Laaz4mORg</field>
+            <field name="name">Awesome Timesheet by Odoo</field>
+            <field name="url">https://www.youtube.com/watch?v=v2O0YZU19ms</field>
             <field name="channel_id" ref="channel_public"/>
             <field name="category_id" ref="category_1"/>
             <field name="website_published" eval="True"/>

addons/website_slides/models/slides.py

@@ -459,7 +459,10 @@ class Slide(models.Model):
             return fetch_res
 
         values = {'slide_type': 'video', 'document_id': document_id}
-        youtube_values = fetch_res['values'].get('items', list(dict()))[0]
+        items = fetch_res['values'].get('items')
+        if not items:
+            return {'error': _('Please enter valid Youtube or Google Doc URL')}
+        youtube_values = items[0]
         if youtube_values.get('snippet'):
             snippet = youtube_values['snippet']
             if only_preview_fields: