DOC Deprecate passing null paramters for Form and ValidationResult me…

…thods

en/08_Changelogs/5.4.0.md

@@ -320,6 +320,17 @@ See [indexes](/developer_guides/model/indexes/) to learn about indexes in Silver
 - The `$join` parameter for the [`Subsite::get_from_all_subsites()`](api:SilverStripe\Subsites\Model\Subsite::get_from_all_subsites()) method has been deprecated. Use [leftJoin($table, $joinClause)](api:SilverStripe\ORM\DataList::leftJoin()) instead.
 - Passing a boolean value to the `$mergeStrategy` argument in [`Form::loadDataFrom()`](api:Silverstripe\Forms\Form::loadDataFrom()) has been deprecated. Pass [`Form::MERGE_CLEAR_MISSING`](api:Silverstripe\Forms\Form::MERGE_CLEAR_MISSING) instead of `true` and `0` instead of `false`.
 - The [`HTTP.ignoreDeprecatedCaching`](api:SilverStripe\Control\HTTP->ignoreDeprecatedCaching) configuration property has been deprecated. It will be removed without equivalent functionality to replace it.
+- Passing `null` for the `$code` parameter in [`ValidationResult::addError()`](api:SilverStripe\ORM\ValidationResult::addError()) is deprecated. Pass a blank string instead.
+- Passing `null` for the `$cast` parameter in [`ValidationResult::addError()`](api:SilverStripe\ORM\ValidationResult::addError()) is deprecated. Pass a ValidationResult::CAST_* constant instead.
+- Passing `null` for the `$code` parameter in [`ValidationResult::addFieldError()`](api:SilverStripe\ORM\ValidationResult::addFieldError()) is deprecated. Pass a blank string instead.
+- Passing `null` for the `$cast` parameter in [`ValidationResult::addFieldError()`](api:SilverStripe\ORM\ValidationResult::addFieldError()) is deprecated. Pass a ValidationResult::CAST_* constant instead.
+- Passing `null` for the `$code` parameter in [`ValidationResult::addMessage()`](api:SilverStripe\ORM\ValidationResult::addMessage()) is deprecated. Pass a blank string instead.
+- Passing `null` for the `$cast` parameter in [`ValidationResult::addMessage()`](api:SilverStripe\ORM\ValidationResult::addMessage()) is deprecated. Pass a ValidationResult::CAST_* constant instead.
+- Passing `null` for the `$code` parameter in [`ValidationResult::addFieldMessage()`](api:SilverStripe\ORM\ValidationResult::addFieldMessage()) is deprecated. Pass a blank string instead.
+- Passing `null` for the `$cast` parameter in [`ValidationResult::addFieldMessage()`](api:SilverStripe\ORM\ValidationResult::addFieldMessage()) is deprecated. Pass a ValidationResult::CAST_* constant instead.
+- Passing `null` for the `$cast` parameter in [`Form::sessionMessage()`](api:SilverStripe\Forms\Form::sessionMessage()) is deprecated. Pass a ValidationResult::CAST_* constant instead.
+- Passing `null` for the `$cast` parameter in [`Form::sessionError()`](api:SilverStripe\Forms\Form::sessionError()) is deprecated. Pass a ValidationResult::CAST_* constant instead.
+- Passing `null` for the `$cast` parameter in [`Form::sessionFieldError()`](api:SilverStripe\Forms\Form::sessionFieldError()) is deprecated. Pass a ValidationResult::CAST_* constant instead.
 
 ## Bug fixes