Remove null option from select widget

This solves a problem with formik not properly handling changing enums
to null. This changes the select widget to always start on the first
option.

arroyo-console/src/routes/connections/JsonForm.tsx

@@ -162,6 +162,12 @@ function SelectWidget({
   value: string;
   onChange: (e: React.ChangeEvent<any>) => void;
 }) {
+  useEffect(() => {
+    if (!value) {
+      onChange({ target: { name: path, value: options[0].value } });
+    }
+  });
+
   return (
     <FormControl isRequired={required}>
       {title && <FormLabel>{title}</FormLabel>}
@@ -470,7 +476,6 @@ export function FormInner({
                       key={key}
                       title={property.title || key}
                       description={property.description}
-                      placeholder="Select an option"
                       required={schema.required?.includes(key)}
                       options={property.enum.map(value => ({
                         value: value!.toString(),
@@ -551,7 +556,6 @@ export function FormInner({
                       <Stack p={4}>
                         <SelectWidget
                           path={typeKey}
-                          placeholder="Select an option"
                           description={property.description}
                           required={schema.required?.includes(key)}
                           options={property.oneOf.map(oneOf => ({