Org Mode Beamer Export

While preparing some lecture notes in Org mode to be exported using Beamer, this error message confused me today and prevented the pdf being built.

! Undefined control sequence.
\beamer@saveanother ->\let \beamer@savedif 
                                           =\ifbeamer@anotherslide

Turns out it was generated by a heading having no content only a tag like this.

* :tagonly: