if dirname is empty, don't add a path separator

contrib/onelab/python/onelab.py

@@ -34,6 +34,7 @@ def path(dirname, inp):
   # dirname is a directory, can be empty
   # inp is an optional file or subdirectory name
   # returns the path to 'inp' in the same directory as 'ref' 
+  if dirname:
     dirname = os.path.dirname(dirname + os.sep)
   if not inp: 
     return dirname