I've installed a debugging plugin for my local WP test environment, and 3 minor notices appeared about WP Google Maps, so here's the fixes for them:
a) Line 281, from:
if (is_admin() && $_GET['page'] == 'wp-google-maps-menu' && $_GET['action'] == "edit_marker") {
to:
if (is_admin() && isset( $_GET['page'] ) && $_GET['page'] == 'wp-google-maps-menu' && $_GET['action'] == "edit_marker") {
b) Line 286, from:
else if (is_admin() && $_GET['page'] == 'wp-google-maps-menu' && $_GET['action'] == "edit") {
to:
else if (is_admin() && isset( $_GET['page'] ) && $_GET['page'] == 'wp-google-maps-menu' && $_GET['action'] == "edit") {
c) Line 1102, from:
if (function_exists(wpgmza_pro_advanced_menu)) {
to:
if (function_exists('wpgmza_pro_advanced_menu')) {
I hope this helps!