Fix errors being thrown when nesting certain components without picking a datasource

packages/standard-components/src/Form.svelte

@@ -14,7 +14,7 @@
   let rowId
   let errors = {}
 
-  $: schema = $store.data && $store.data._table.schema
+  $: schema = $store.data && $store.data._table && $store.data._table.schema
   $: fields = schema ? Object.keys(schema) : []
 </script>
 

packages/standard-components/src/NewRow.svelte

@@ -19,7 +19,7 @@
   }
 
   onMount(async () => {
-    if (table) {
+    if (table && typeof table === "string") {
       const tableObj = await fetchTable(table)
       row.tableId = table
       row._table = tableObj