Use Optional validator for BA code

atst/forms/financial.py

@@ -2,7 +2,7 @@ import re
 import pendulum
 from wtforms.fields.html5 import DateField, EmailField
 from wtforms.fields import StringField, FileField
-from wtforms.validators import InputRequired, Required, Email, Regexp
+from wtforms.validators import InputRequired, Required, Optional, Email, Regexp
 from flask_wtf.file import FileAllowed
 
 from atst.domain.exceptions import NotFoundError
@@ -123,7 +123,7 @@ class BaseFinancialForm(ValidatedForm):
     ba_code = StringField(
         "Program Budget Activity (BA) Code (Optional)",
         description="BA Code is used to identify the purposes, projects, or types of activities financed by the appropriation fund. <br/><em>It should be two digits, followed by an optional letter.</em>",
-        validators=[Regexp(BA_CODE_REGEX)],
+        validators=[Optional(), Regexp(BA_CODE_REGEX)],
     )
 
     fname_co = StringField("KO First Name", validators=[Required()])

tests/forms/test_financial.py

@@ -74,8 +74,8 @@ def test_treasury_code_validation(input_, expected):
     ],
 )
 def test_ba_code_validation(input_, expected):
-    form_data = {"ba_code": input_}
-    form = FinancialForm(data=form_data)
+    form_data = ImmutableMultiDict([("ba_code", input_)])
+    form = FinancialForm(form_data)
     form.validate()
     is_valid = "ba_code" not in form.errors