Anyone with a newer Dell laptop (the black touchscreen ones) should have an application called Dell Command Update on it – type Dell into your Start menu and it should appear there. Run this and check for updates. If you see a big orange warning mentioning temporarily suspending Bitlocker before being able to install updates, please do this. There is a link to the Control Panel here:
Click on this and then Suspend protection here:
Once you've done this, go back to the Dell Command Update window and the Critical Updates box should have ticked itself. Click on the big blue Install button in the bottom right. Note that your computer will restart itself unless you untick the box giving it permission to do so.
Once updates have been applied and you've restarted Bitlocker will turn itself back on.
Please then check for updates once more to make sure nothing else is available.
Shout if help is required.