Source

beamer / base / beamerbaseframe.sty

Diff from to

File base/beamerbaseframe.sty

     \beamer@slideinframe=0\relax%
     \beamer@anotherslidefalse%
     {\beamer@masterdecode{#1}}%
+    \show\ifbeamer@anotherslide
     \ifbeamer@anotherslide%
       \let\beamer@howtotreatframe\beamer@dosingleframe%
     \else% no slides in frame