Update TO route helper function to catch error and display flash message when a user tries to save a TO with an existing number.

Update TaskOrderForm so that it converts empty string for number into None, this was causing an issue where new TOs were being saved with an empty string for the number, which violated the unique constraint.

tests/forms/test_task_order.py

@@ -2,7 +2,7 @@ import datetime
 from dateutil.relativedelta import relativedelta
 from flask import current_app as app
 
-from atst.forms.task_order import CLINForm
+from atst.forms.task_order import CLINForm, TaskOrderForm
 from atst.models import JEDICLINType
 from atst.utils.localization import translate
 
@@ -106,3 +106,9 @@ def test_clin_form_dollar_amounts_out_of_range():
     assert (
         translate("forms.task_order.clin_funding_errors.funding_range_error")
     ) in invalid_clin_form.obligated_amount.errors
+
+
+def test_no_number():
+    http_request_form_data = {}
+    form = TaskOrderForm(http_request_form_data)
+    assert form.data["number"] is None