message: fix(dropdown): bootstrap 4 dropup fix in IE11
  The inline style on the element is top: auto, this fix is for cross browser support.
  Fixes
diff: @@ -318,8 +318,6 @@ export class BsDropdownDirective implements OnInit, OnDestroy {
  private checkDropup(): void {
  if (this._inlinedMenu && this._inlinedMenu.rootNodes[0]) {
  // a little hack to not break support of bootstrap 4 beta
  - const top = getComputedStyle(this._inlinedMenu.rootNodes[0]).top;
  - const topAuto = top === 'auto' || top === '100%';
  this._renderer.setStyle(
  this._inlinedMenu.rootNodes[0],
  'top',
  @@ -328,7 +326,7 @@ export class BsDropdownDirective implements OnInit, OnDestroy {
  this._renderer.setStyle(
  this._inlinedMenu.rootNodes[0],
  'transform',
  - this.dropup && !topAuto ? 'translateY(-101%)' : 'translateY(0)'
  + this.dropup ? 'translateY(-101%)' : 'translateY(0)'
  );
  }
  }
  