Impacted versions:
9.0 Community & 9.0 Enterprise

Steps to reproduce:
- Open up a V9 runbot
- Go to projects and click on the issues item, for example for the project 'Research & Development':
  ![image](https://cloud.githubusercontent.com/assets/6352350/13873686/65f2c31c-ecf3-11e5-917a-38df2832bd00.png)
- The project tasks view is opened in place of the project issues. (notice that this only happens every once in a while, about once in five attempts) Example:
  ![image](https://cloud.githubusercontent.com/assets/6352350/13873789/14798b64-ecf4-11e5-9b77-f2ad5d3a8adc.png)

Current behavior:
Every once in a while (about one out of five attempts) after clicking on the issues button it will open up the project tasks, not the issues.

Expected behavior:
When you click on the issues the view with all issues opens, not the view for all tasks.

if not task_id:
            return {'value': {}}
        task = self.pool.get('project.task').browse(cr, uid, task_id, context=context)
        return {'value': {'user_id': task.user_id.id, }}
    def onchange_partner_id(self, cr, uid, ids, partner_id, context=None):
        """ This function returns value of partner email address based on partner
            :param part: Partner's id
        """
        if partner_id:
            partner = self.pool['res.partner'].browse(cr, uid, partner_id, context)
            return {'value': {'email_from': partner.email}}
        return {'value': {'email_from': False}}
    def get_empty_list_help(self, cr, uid, help, context=None):
        context = dict(context or {})
        context['empty_list_help_model'] = 'project.project'
        context['empty_list_help_id'] = context.get('default_project_id')
        context['empty_list_help_document_name'] = _("issues")
        return super(project_issue, self).get_empty_list_help(cr, uid, help, context=context)
    # --
    # St
    # --
    def onchange_stage_id(self, cr, uid, ids, stage_id, context=None):
        if not stage_id:
            return {'value': {}}
        stage = self.pool['project.task.type'].browse(cr, uid, stage_id, context=context)
        if stage.fold:
            return {'value': {'date_closed': fields.datetime.now()}}
        return {'value': {'date_closed': False}}
    def stage_find(self, cr, uid, cases, team_id, domain=[], order='sequence', context=None):
        """ Override of the base.stage method