Hidden subsections cause space between entries in table of contents

When hiding the subsections in the table of contents via \setcounter{tocdepth}{1}, each subsection causes a space to be added between the entries for the sections.

This problem can be circumvented by removing the following lines from the beamerthemetuhh.sty:

\pretocmd{\beamer@subsectionintoc}
  {\vskip 0.25em}
  {}
  {}