[FIX] report: Traceback on print report from wizard.

Go to Product Variant  >> Select any Product Variant >> Print Report Of Price List >> select any Price List
and Click on print button it's gives traceback like:
http://www.awesomescreenshot.com/image/1288867/b6639baf8cb94e3a90ce9d347b3f4f35

Introduced by https://github.com/odoo/odoo/commit/da3d2fb1dc76654e630fba27ca3dcf03002d9431

addons/report/controllers/main.py

@@ -104,10 +104,11 @@ class ReportController(Controller):
                 cr, uid = request.cr, request.uid
                 report = request.registry['report']._get_report_from_name(cr, uid, reportname)
                 filename = "%s.%s" % (report.name, "pdf")
-                ids = [int(x) for x in docids.split(",")]
-                obj = request.env[report.model].browse(ids)
-                if report.print_report_name and not len(obj) > 1:
-                    filename = eval(report.print_report_name, {'object': obj, 'time': time})
+                if docids:
+                    ids = [int(x) for x in docids.split(",")]
+                    obj = request.env[report.model].browse(ids)
+                    if report.print_report_name and not len(obj) > 1:
+                        filename = eval(report.print_report_name, {'object': obj, 'time': time})
                 response.headers.add('Content-Disposition', content_disposition(filename))
                 response.set_cookie('fileToken', token)
                 return response