Fix flow graph input step preview (#4265)

frontend/src/lib/components/FlowGraphViewer.svelte

@@ -37,7 +37,7 @@
 				modules={flow?.value?.modules}
 				failureModule={flow?.value?.failure_module}
 				on:select={(e) => {
-					const mod = dfs(flow?.value?.modules, (m) => m).find((m) => m?.id === e?.detail)
+					const mod = dfs(flow?.value?.modules ?? [], (m) => m).find((m) => m?.id === e?.detail)
 					stepDetail = mod ?? e.detail
 					dispatch('select', stepDetail)
 				}}

frontend/src/routes/(root)/(logged)/flows/get/[...path]/+page.svelte

@@ -437,7 +437,7 @@
 						overflowAuto
 						noSide={true}
 						on:select={(e) => {
-							if (e.detail.id) {
+							if (e.detail) {
 								stepDetail = e.detail
 							} else {
 								stepDetail = undefined