[fields] Fix oneOf/anyOf fields

Author: x0k

.changeset/tangy-queens-doubt.md

@@ -0,0 +1,5 @@
+---
+"@sjsf/form": patch
+---
+
+Fix oneOf/anyOf fields

packages/form/src/fields/combination.svelte

@@ -64,8 +64,8 @@
     const restType = getSimpleSchemaType(restSchema);
     return {
       ...config,
-      schema: restType === "unknown" ? {} : restSchema,
-    };
+      schema: restType === "unknown" ? { type: "object" } : restSchema,
+    } satisfies Config;
   });
   const RestSchemaField = $derived(
     restFieldConfig && getFieldComponent(ctx, restFieldConfig)