Popover directive throws error if [skyPopover] is undefined

[Blackbaud-SteveBrush]

This will cause an error in the console:

<button
  type="button"
  class="sky-btn sky-btn-default"
  [skyPopover]="undefined">
  Open popover
</div>

<sky-popover #disabledInfo>
  Content.
</sky-popover>