Prevent outro from invoking detach multiple times

src/runtime/internal/keyed-each.ts

@@ -1,13 +1,17 @@
 import { transition_in, transition_out } from './transitions';
 
+export function remove_block_from_lookup(block, lookup) {
+	lookup.delete(block.key);
+}
+
 export function destroy_block(block, lookup) {
 	block.d(1);
-	lookup.delete(block.key);
+	remove_block_from_lookup(block, lookup);
 }
 
 export function outro_and_destroy_block(block, lookup) {
 	transition_out(block, 1, () => {
-		destroy_block(block, lookup);
+		remove_block_from_lookup(block, lookup);
 	});
 }