Fix b791ffc6: use the correct parameter in CmdSignalTrackHelper

src/rail_cmd.cpp

@@ -1381,15 +1381,15 @@ static CommandCost CmdSignalTrackHelper(TileIndex tile, DoCommandFlag flags, uin
 				last_suitable_trackdir = trackdir;
 			} else if (!test_only && last_suitable_tile != INVALID_TILE) {
 				/* If a signal can't be placed, place it at the last possible position. */
-				SB(p1, 0, 3, TrackdirToTrack(last_suitable_trackdir));
-				ClrBit(p1, 17);
+				SB(param1, 0, 3, TrackdirToTrack(last_suitable_trackdir));
+				ClrBit(param1, 17);
 
 				/* Pick the correct orientation for the track direction. */
 				signals = 0;
 				if (HasBit(signal_dir, 0)) signals |= SignalAlongTrackdir(last_suitable_trackdir);
 				if (HasBit(signal_dir, 1)) signals |= SignalAgainstTrackdir(last_suitable_trackdir);
 
-				ret = DoCommand(last_suitable_tile, p1, signals, flags, remove ? CMD_REMOVE_SIGNALS : CMD_BUILD_SIGNALS);
+				ret = DoCommand(last_suitable_tile, param1, signals, flags, remove ? CMD_REMOVE_SIGNALS : CMD_BUILD_SIGNALS);
 			}
 
 			/* Collect cost. */