Fix clearSelection in select all mode

src/SelectionModel.ts

@@ -32,6 +32,15 @@ export class SelectionModel {
   ) {
   }
 
+  /**
+   * Clears the current selection.
+   */
+  public clearSelection(): void {
+    this.selectionStart = null;
+    this.selectionEnd = null;
+    this.isSelectAllActive = false;
+  }
+
   /**
    * The final selection start, taking into consideration select all.
    */