qidoc: fix crash when build_type is None
qidoc: fix crash when build_type is None

Change-Id: I7aa08d537b4ecd30b62df3d32aec9593675149ea

dmerejkowsky/qibuild,dmerejkowsky/qibuild,aldebaran/qibuild,aldebaran/qibuild,aldebaran/qibuild,dmerejkowsky/qibuild,dmerejkowsky/qibuild,dmerejkowsky/qibuild,aldebaran/qibuild