sysdeps-win: Fix autolaunch: regression on Windows
Commit f20a05f6 included in dbus-1.15.0 broke autolaunch: on Windows. autolaunch_custom_command_line_parameter shall be initalized to null as it is later used in only one place in the code, with this ternary:
autolaunch_custom_command_line_parameter ? autolaunch_custom_command_line_parameter : "--session"
Closes #503 (closed)