Hi,

I did the following:

1.) installed GMap Module dev version (16th April 2013) and Location module (current stable version)
2.) created some nodes with Location information
3.) created a view showing these nodes in a map: Gmap style,
4.) checked "Center on proximity contextual filter" (such a filter is in the view

When this option is checked everything works but an error message appears:

Notice: Trying to get property of non-object in gmap_plugin_style_gmap->render() (Line 168 of C:\wamp\www\project\sites\all\modules\gmap\gmap_plugin_style_gmap.inc).
Notice: Trying to get property of non-object in gmap_plugin_style_gmap->render() (Line 169 of C:\wamp\www\project\sites\all\modules\gmap\gmap_plugin_style_gmap.inc).

Best,
Tobias