GPS: guard against empty command strings in the route-manager.

diff --git a/src/Autopilot/route_mgr.cxx b/src/Autopilot/route_mgr.cxx
index bbd2db96b58531c063ecbee448a26ee897395420..45e3c922ff36e978fc0495b5f5f69e685018d17c 100644 (file)
--- a/src/Autopilot/route_mgr.cxx
+++ b/src/Autopilot/route_mgr.cxx
@@ -455,6 +455,10 @@ void FGRouteMgr::update_mirror() {
 void FGRouteMgr::InputListener::valueChanged(SGPropertyNode *prop)
 {
     const char *s = prop->getStringValue();
+    if (strlen(s) == 0) {
+      return;
+    }
+    
     if (!strcmp(s, "@CLEAR"))
         mgr->init();
     else if (!strcmp(s, "@ACTIVATE"))