Let us split a check for a condition at the beginning of the
batadv_is_ap_isolated() function so that a direct return can be performed
in this function if the variable "vlan" contained a null pointer.
Signed-off-by: Markus Elfring <elfring@users.sourceforge.net> Signed-off-by: Marek Lindner <mareklindner@neomailbox.ch> Signed-off-by: Antonio Quartulli <a@unstable.cc>