Cannot save new assessment in ERPnext school

When i try to save a new assessment. I get the following errorr `Please type some additional information that could help us reproduce this issue:
App Versions

{
	"erpnext": "7.2.14",
	"frappe": "7.2.13"
}

Route

Form/Assessment/New Assessment 2

Error Report

Traceback (most recent call last):
  File "/home/frappe/frappe-bench/apps/frappe/frappe/desk/form/save.py", line 22, in savedocs
    doc.save()
  File "/home/frappe/frappe-bench/apps/frappe/frappe/model/document.py", line 223, in save
    return self._save(*args, **kwargs)
  File "/home/frappe/frappe-bench/apps/frappe/frappe/model/document.py", line 242, in _save
    self.insert()
  File "/home/frappe/frappe-bench/apps/frappe/frappe/model/document.py", line 189, in insert
    self.run_before_save_methods()
  File "/home/frappe/frappe-bench/apps/frappe/frappe/model/document.py", line 750, in run_before_save_methods
    self.run_method("validate")
  File "/home/frappe/frappe-bench/apps/frappe/frappe/model/document.py", line 651, in run_method
    out = Document.hook(fn)(self, *args, **kwargs)
  File "/home/frappe/frappe-bench/apps/frappe/frappe/model/document.py", line 858, in composer
    return composed(self, method, *args, **kwargs)
  File "/home/frappe/frappe-bench/apps/frappe/frappe/model/document.py", line 841, in runner
    add_to_return_value(self, fn(self, *args, **kwargs))
  File "/home/frappe/frappe-bench/apps/frappe/frappe/model/document.py", line 645, in 
    fn = lambda self, *args, **kwargs: getattr(self, method)(*args, **kwargs)
  File "/home/frappe/frappe-bench/apps/erpnext/erpnext/schools/doctype/assessment/assessment.py", line 12, in validate
    self.validate_overlap()
  File "/home/frappe/frappe-bench/apps/erpnext/erpnext/schools/doctype/assessment/assessment.py", line 37, in validate_overlap
    validate_overlap_for(self, "Assessment", "supervisor", self.instructor)
AttributeError: 'Assessment' object has no attribute 'instructor'

Traceback (most recent call last):
  File "/home/frappe/frappe-bench/apps/frappe/frappe/app.py", line 55, in application
    response = frappe.handler.handle()
  File "/home/frappe/frappe-bench/apps/frappe/frappe/handler.py", line 19, in handle
    execute_cmd(cmd)
  File "/home/frappe/frappe-bench/apps/frappe/frappe/handler.py", line 40, in execute_cmd
    ret = frappe.call(method, **frappe.form_dict)
  File "/home/frappe/frappe-bench/apps/frappe/frappe/__init__.py", line 897, in call
    return fn(*args, **newargs)
  File "/home/frappe/frappe-bench/apps/frappe/frappe/desk/form/save.py", line 22, in savedocs
    doc.save()
  File "/home/frappe/frappe-bench/apps/frappe/frappe/model/document.py", line 223, in save
    return self._save(*args, **kwargs)
  File "/home/frappe/frappe-bench/apps/frappe/frappe/model/document.py", line 242, in _save
    self.insert()
  File "/home/frappe/frappe-bench/apps/frappe/frappe/model/document.py", line 189, in insert
    self.run_before_save_methods()
  File "/home/frappe/frappe-bench/apps/frappe/frappe/model/document.py", line 750, in run_before_save_methods
    self.run_method("validate")
  File "/home/frappe/frappe-bench/apps/frappe/frappe/model/document.py", line 651, in run_method
    out = Document.hook(fn)(self, *args, **kwargs)
  File "/home/frappe/frappe-bench/apps/frappe/frappe/model/document.py", line 858, in composer
    return composed(self, method, *args, **kwargs)
  File "/home/frappe/frappe-bench/apps/frappe/frappe/model/document.py", line 841, in runner
    add_to_return_value(self, fn(self, *args, **kwargs))
  File "/home/frappe/frappe-bench/apps/frappe/frappe/model/document.py", line 645, in 
    fn = lambda self, *args, **kwargs: getattr(self, method)(*args, **kwargs)
  File "/home/frappe/frappe-bench/apps/erpnext/erpnext/schools/doctype/assessment/assessment.py", line 12, in validate
    self.validate_overlap()
  File "/home/frappe/frappe-bench/apps/erpnext/erpnext/schools/doctype/assessment/assessment.py", line 37, in validate_overlap
    validate_overlap_for(self, "Assessment", "supervisor", self.instructor)
AttributeError: 'Assessment' object has no attribute 'instructor'

Request Data

{
	"type": "POST",
	"args": {
		"doc": "{\"docstatus\":0,\"doctype\":\"Assessment\",\"name\":\"New Assessment 2\",\"__islocal\":1,\"__unsaved\":1,\"owner\":\"faraja@jofarsystems.com\",\"schedule_date\":\"2017-01-27\",\"from_time\":\"12:18:19\",\"to_time\":\"14:18:19\",\"assessment_name\":\"End term\",\"assessment_code\":\"008\",\"course\":\"FRANÇAIS\",\"student_group\":\"FRANÇAIS-COURS GENERAUX-Class 8-2017-18-2017-18 (Semester 1)\",\"results\":[{\"docstatus\":0,\"doctype\":\"Assessment Result\",\"name\":\"New Assessment Result 1\",\"__islocal\":1,\"__unsaved\":1,\"owner\":\"faraja@jofarsystems.com\",\"parent\":\"New Assessment 2\",\"parentfield\":\"results\",\"parenttype\":\"Assessment\",\"idx\":1,\"student\":\"STUD00001\",\"student_name\":\"James Ndoto\",\"result\":\"65\"}],\"student_batch\":\"COURS GENERAUX-Class 8-2017-18\",\"grading_structure\":\"Test\",\"assessment_group\":\"Class 8\",\"supervisor_name\":\"Paul Mukobelwa\",\"supervisor\":\"INS/00001\",\"examiner_name\":\"Simwera Kabongoli\",\"examiner\":\"INS/00002\",\"room\":\"RM0001\"}",
		"action": "Save",
		"cmd": "frappe.desk.form.save.savedocs"
	},
	"btn": {
		"jQuery2240123565686052344971": {
			"events": {
				"click": [
					{
						"type": "click",
						"origType": "click",
						"guid": 3080,
						"namespace": ""
					}
				]
			}
		}
	},
	"freeze": true,
	"freeze_message": "Saving",
	"url": "/"
}

Response JSON

{
	"_server_messages": "[\"{\\\"message\\\": \\\"Did not save\\\"}\"]"
}`

@neilLasrado @rmehta anyone?

@Mute can you please update your instance. ( bench update) we have fixed the issue in the upcoming version and have also redesigned the entire assessment module.