Fix removing profile details (Closes #894) (#899)

* Fix removing profile details (Closes #894)
* Update tests to properly check setting and removing profile values

tests/utils/test_validators.py

@@ -0,0 +1,11 @@
+from CTFd.utils.validators import validate_country_code
+from marshmallow import ValidationError
+
+
+def test_validate_country_code():
+    assert validate_country_code('') is None
+    # TODO: This looks poor, when everything moves to pytest we should remove exception catches like this.
+    try:
+        validate_country_code('ZZ')
+    except ValidationError:
+        pass