Exception while upgrade problem with patches.v8_1.set_delivery_date_in_so_item

i’m getting following exception in patch while upgrading.

every time i have to skip this patch to upgrade bench.

Executing erpnext.patches.v8_1.set_delivery_date_in_so_item #2017-07-28

Exception:

File “/home/frappe/frappe-bench/env/local/lib/python2.7/site-packages/pymysql/err.py”, line 107, in raise_mysql_exception
raise errorclass(errno, errval)
pymysql.err.InternalError: (1292, u"Incorrect datetime value: ‘’")

need a fix for this patch

Please post your request for a fix https://github.com/frappe/erpnext/issues