Fix minor bug in BlocklyRequestHandler:

When the Sketch path was changed the server was returning the new address in plain text instead of JSON. Updated to send the correct JSON data.

ArduinoServerCompiler/BlocklyRequestHandler.py

@@ -354,7 +354,7 @@ def set_sketch_path():
     new_directory = browse_dir()
     if new_directory != '':
         ServerCompilerSettings().sketch_dir = new_directory
-    return new_directory
+    return get_sketch_path()
 
 
 def get_sketch_path():