move unset_context call

Author: Rich-Harris

packages/svelte/src/internal/client/reactivity/deriveds.js

@@ -126,9 +126,11 @@ export function async_derived(fn, location) {
 		try {
 			// If this code is changed at some point, make sure to still access the then property
 			// of fn() to read any signals it might access, so that we track them as dependencies.
+			// We call `unset_context` to undo any `save` calls that happen inside `fn()`
 			Promise.resolve(fn()).then(d.resolve, d.reject).then(unset_context);
 		} catch (error) {
 			d.reject(error);
+			unset_context();
 		}
 
 		if (DEV) current_async_effect = null;
@@ -185,8 +187,6 @@ export function async_derived(fn, location) {
 				boundary.update_pending_count(-1);
 				if (!pending) batch.decrement();
 			}
-
-			unset_context();
 		};
 
 		d.promise.then(handler, (e) => handler(null, e || 'unknown'));