APM_OBC: don't use _saved_wp when zero

libraries/APM_OBC/APM_OBC.cpp

@@ -130,7 +130,10 @@ APM_OBC::check(APM_OBC::control_mode mode,
 		} else if (gcs_link_ok) {
 			_state = STATE_AUTO;
 			gcs_send_text_fmt(PSTR("GCS OK"));
-			change_command(_saved_wp);			
+			if (_saved_wp != 0) {
+				change_command(_saved_wp);			
+				_saved_wp = 0;
+			}
 		}
 		break;
 
@@ -143,7 +146,10 @@ APM_OBC::check(APM_OBC::control_mode mode,
 		} else if (gps_lock_ok) {
 			gcs_send_text_fmt(PSTR("GPS OK"));
 			_state = STATE_AUTO;
-			change_command(_saved_wp);			
+			if (_saved_wp != 0) {
+				change_command(_saved_wp);			
+				_saved_wp = 0;
+			}
 		}
 		break;
 	}

libraries/APM_OBC/APM_OBC.h

@@ -43,6 +43,7 @@ public:
 		// auto mission when a failsafe condition is resolved
 		enum ap_var_type var_type;
 		_command_index = (AP_Int8 *)AP_Param::find("CMD_INDEX", &var_type);
+		_saved_wp = 0;
 	}
 
 	void check(enum control_mode control_mode,