improve conditional

src/common/buffer/Buffer.ts

@@ -625,7 +625,7 @@ export class Buffer implements IBuffer {
   }
 
   private _removeMarker(marker: Marker): void {
-    if (this._isClearing !== BufferState.CLEARING) {
+    if (!this._isClearing) {
       this.markers.splice(this.markers.indexOf(marker), 1);
     }
   }