Python code:

def openVideo(self):
    video_url = self._context.get('url') # yes, this have a value
    return {
        'type': 'ir.actions.act_window',
        'name': 'Video',
        'res_model': 'ir.ui.view',
        'view_mode': 'form',
        'context': {
            **self._context,
            'default_video_url': video_url
        },
        'view_id': self.env.ref('tms_manual_sistema.video_popup').id,
        'target': 'new',

    }

Template:

<odoo>
    <data>
    <template id="tms_manual_sistema.video_popup">
        <div>
        <t t-if="context.get('default_video_url')">
            <p>Video URL: <t t-esc="context.get('default_video_url')"/></p>
        </t>
        <t t-else="">
            <p>No video URL provided</p>
        </t>
        </div>
        <div class="o_notification o_notification_warning">
             <div class="oe_video">
                 <iframe width="560" height="315" t-att-src="context.get('default_video_url')" frameborder="0" allowfullscreen="true"/>
             </div>
        </div>
    </template>
    </data>
</odoo>

Always shows "No Video URL provided". What i did wrong?