fix(editor): block can be null in widget (#10959)

Closes: [BS-2826](https://linear.app/affine-design/issue/BS-2826/typeerror-thisblock-is-null)

blocksuite/affine/widgets/widget-drag-handle/src/watchers/pointer-event-watcher.ts

@@ -161,6 +161,8 @@ export class PointerEventWatcher {
     if (this.widget.isGfxDragHandleVisible) return;
 
     const point = new Point(state.raw.x, state.raw.y);
+    if (!this.widget.rootComponent) return;
+
     const closestBlock = getClosestBlockByPoint(
       this.widget.host,
       this.widget.rootComponent,
@@ -246,6 +248,8 @@ export class PointerEventWatcher {
       // When pointer on drag handle, should do nothing
       if (element.closest('.affine-drag-handle-container')) return;
 
+      if (!this.widget.rootComponent) return;
+
       // When pointer out of note block hover area or inside database, should hide drag handle
       const point = new Point(state.raw.x, state.raw.y);
 

blocksuite/affine/widgets/widget-edgeless-auto-connect/src/index.ts

@@ -284,6 +284,9 @@ export class EdgelessAutoConnectWidget extends WidgetComponent<RootBlockModel> {
   }
 
   private _initLabels() {
+    if (!this.block) {
+      return;
+    }
     const { service } = this.block;
     const surfaceRefs = service.doc
       .getBlocksByFlavour('affine:surface-ref')

blocksuite/affine/widgets/widget-remote-selection/src/doc/doc-remote-selection.ts

@@ -144,6 +144,10 @@ export class AffineDocRemoteSelectionWidget extends WidgetComponent {
   }
 
   private _getCursorRect(selections: BaseSelection[]): SelectionRect | null {
+    if (!this.block) {
+      return null;
+    }
+
     if (this.block.model.flavour !== 'affine:page') {
       console.error('remote selection widget must be used in page component');
       return null;
@@ -208,6 +212,10 @@ export class AffineDocRemoteSelectionWidget extends WidgetComponent {
   private readonly _getSelectionRect = (
     selections: BaseSelection[]
   ): SelectionRect[] => {
+    if (!this.block) {
+      return [];
+    }
+
     if (this.block.model.flavour !== 'affine:page') {
       console.error('remote selection widget must be used in page component');
       return [];

blocksuite/affine/widgets/widget-slash-menu/src/widget.ts

@@ -105,7 +105,7 @@ export class AffineSlashMenuWidget extends WidgetComponent {
       }
     };
 
-    if (this.block.model.flavour !== 'affine:page') {
+    if (this.block?.model.flavour !== 'affine:page') {
       console.error('SlashMenuWidget should be used in RootBlock');
       return;
     }