Two solutions I can think of.
Probably a Startup script (Python or Tcl) would do the job. You could create a script to examine the source file parameters to determine what type of data is being read.
Alternatively, use the GeometryFilter to determine whether the data is spatial or tabular, and then connect the output to a WorkspaceRunner to run a different workspace depending on the geometry type. A Sampler transformer would let you reduce it to testing a single feature, to speed things up and ensure the workspaceRunner is only triggered once.
Hope this helps
Mark
Mark Ireland
Product Evangelist
Safe Software Inc.