fix(frontend): prevent Select.Item crash on empty-string enum values

Radix UI's Select.Item throws when value="". The SelectWidget used
value={value ?? ""} which passes empty string for null/undefined form
values, and passed enum options through without filtering.

- Use value || undefined to show placeholder for unset values
- Filter out empty-string options before rendering SelectItems

Resolves SECRT-2157

autogpt_platform/frontend/src/components/renderers/InputRenderer/base/standard/widgets/SelectInput/SelectWidget.tsx

@@ -61,13 +61,15 @@ export const SelectWidget = (props: WidgetProps) => {
         hideLabel={true}
         disabled={disabled || readonly}
         size={selectSize as any}
-        value={value ?? ""}
+        value={value || undefined}
         onValueChange={onChange}
         options={
-          enumOptions?.map((option: any) => ({
-            value: option.value,
-            label: option.label,
-          })) || []
+          enumOptions
+            ?.filter((option: any) => option.value !== "")
+            .map((option: any) => ({
+              value: option.value,
+              label: option.label,
+            })) || []
         }
         wrapperClassName="!mb-0 "
         className={className}