Issue #1077850 by silverflame757, garrettrayj: Fixed Empty View with...

Issue #1077850 by silverflame757, garrettrayj: Fixed Empty View with DataSource Choose latitude and longitude fields ( GMap + Views ) .

gmap.views.inc

@@ -64,6 +64,9 @@ function template_preprocess_gmap_views_view_gmapextended(&$vars) {
   foreach ($renders as $i => $row) {
     $markers[$i] = $options['fallback_values'];
     foreach ($options['field_purposes'] as $field => $purpose) {
+      if (!isset($markers[$i][$purpose])) {
+        $markers[$i][$purpose] = '';
+      }
       $markers[$i][$purpose] .= $row[$field];
     }
   }