chore: allow `null` for `pending` in typings (#18201)

Closes #18166

We handle all falsy values at runtime already and for basically every
other dom attribute also allow `null`, so no reason not to do this.

.changeset/fine-bushes-marry.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+chore: allow `null` for `pending` in typings

packages/svelte/elements.d.ts

@@ -2067,9 +2067,9 @@ export interface SvelteHTMLElements {
 	};
 	'svelte:head': { [name: string]: any };
 	'svelte:boundary': {
-		onerror?: (error: unknown, reset: () => void) => void;
+		onerror?: ((error: unknown, reset: () => void) => void) | null | undefined;
-		failed?: import('svelte').Snippet<[error: unknown, reset: () => void]>;
+		failed?: import('svelte').Snippet<[error: unknown, reset: () => void]> | null | undefined;
-		pending?: import('svelte').Snippet;
+		pending?: import('svelte').Snippet | null | undefined;
 	};
 
 	[name: string]: { [name: string]: any };

packages/svelte/src/internal/client/dom/blocks/boundary.js

@@ -35,19 +35,18 @@ import { queue_micro_task } from '../task.js';
 import * as e from '../../errors.js';
 import * as w from '../../warnings.js';
 import { DEV } from 'esm-env';
-import { Batch, current_batch, previous_batch, schedule_effect } from '../../reactivity/batch.js';
+import { Batch, current_batch } from '../../reactivity/batch.js';
 import { internal_set, source } from '../../reactivity/sources.js';
 import { tag } from '../../dev/tracing.js';
 import { createSubscriber } from '../../../../reactivity/create-subscriber.js';
 import { create_text } from '../operations.js';
 import { defer_effect } from '../../reactivity/utils.js';
-import { set_signal_status } from '../../reactivity/status.js';
 
 /**
  * @typedef {{
- * 	 onerror?: (error: unknown, reset: () => void) => void;
+ * 	 onerror?: ((error: unknown, reset: () => void) => void) | null;
- *   failed?: (anchor: Node, error: () => unknown, reset: () => () => void) => void;
+ *   failed?: ((anchor: Node, error: () => unknown, reset: () => () => void) => void) | null;
- *   pending?: (anchor: Node) => void;
+ *   pending?: ((anchor: Node) => void) | null;
  * }} BoundaryProps
  */