message: Fixed incorrect checks in configured canvas handlers
  this.state is a method so it always exists, but this._state is a property that might be null
diff: @@ -850,7 +850,7 @@ export class PaneWidget implements IDestroyable, MouseEventHandlers {
  }
  private readonly _canvasConfiguredHandler = () => {
  - if (this._isSettingSize || !this.state) {
  + if (this._isSettingSize || this._state === null) {
  return;
  }
  @@ -858,7 +858,7 @@ export class PaneWidget implements IDestroyable, MouseEventHandlers {
  };
  private readonly _topCanvasConfiguredHandler = () => {
  - if (this._isSettingSize || !this.state) {
  + if (this._isSettingSize || this._state === null) {
  return;
  }
  