🐛 [open-formulieren/open-forms#4659] Ensure that textfield have a val…

…id empty value

src/components/formio/textfield.tsx

@@ -1,6 +1,6 @@
 import clsx from 'clsx';
 import {Field, useFormikContext} from 'formik';
-import {useContext, useRef} from 'react';
+import {useContext, useEffect, useRef} from 'react';
 
 import {RenderContext} from '@/context';
 import CharCount from '@/utils/charcount';
@@ -35,7 +35,7 @@ export const TextField: React.FC<JSX.IntrinsicElements['input'] & TextFieldProps
   childrenAfterField,
   ...props
 }) => {
-  const {getFieldProps, getFieldMeta} = useFormikContext();
+  const {getFieldProps, getFieldMeta, setFieldValue} = useFormikContext();
   const {value, onChange: formikOnChange} = getFieldProps<string | undefined>(name);
   const {touched} = getFieldMeta<string | undefined>(name);
   const {errors, hasErrors} = useValidationErrors(name);
@@ -48,6 +48,14 @@ export const TextField: React.FC<JSX.IntrinsicElements['input'] & TextFieldProps
     props = {...props, value: ''};
   }
 
+  useEffect(() => {
+    if (value === undefined || value === null) {
+      // Make sure value is valid
+      setFieldValue(name, '');
+    }
+  }, [value]);
+
+
   // XXX: this is only accepted in the form builder to get to (close to) vanilla form
   // builder feature parity - setting the value with mask placeholders is bad for
   // accessibility.