Same for me, the patch #7 with 2.0.9 solves the Session error.
This is the case with the patch, the "Search extra value" is not visible by the user.
If you open the debugger tools of your browser and go under the Network tab you can see the "extra value" added to the query while typing text in the autocomplete field, nothing else...
Tell me if I'm wrong but there is nothing in code about location_bias_scale...
For me the "Search extra value" is optional and meant to add limitation in results returned by the autocomplete field.
For example if I'm typing "vev" in autocomplete, I don't want that appears results from Germany or Czechoslovakia but only from Switzerland or any "Search extra value" set. With this example if I set "Vaud Switzerland" in "Search extra value", while I'm typing "vev" in autocomplete the photon API search for "q=vev Vaud Switzerland" and I'm getting only results in this particular region (Vaud) in Switzerland.
Just leaving "Search extra value" empty gives the default behavior.
Maybe I'm missing something...