(svn r22638) -Fix: Keep the previous owner of the upper and lower lock parts if they are built on existing water.

src/water_cmd.cpp

@@ -279,8 +279,8 @@ static CommandCost RemoveLock(TileIndex tile, DoCommandFlag flags)
 
 	if (flags & DC_EXEC) {
 		DoClearSquare(tile);
-		MakeWaterKeepingClass(tile + delta, GetTileOwner(tile));
-		MakeWaterKeepingClass(tile - delta, GetTileOwner(tile));
+		MakeWaterKeepingClass(tile + delta, GetTileOwner(tile + delta));
+		MakeWaterKeepingClass(tile - delta, GetTileOwner(tile - delta));
 		MarkCanalsAndRiversAroundDirty(tile - delta);
 		MarkCanalsAndRiversAroundDirty(tile + delta);
 	}

src/water_map.h

@@ -421,8 +421,10 @@ static inline void MakeLock(TileIndex t, Owner o, DiagDirection d, WaterClass wc
 	TileIndexDiff delta = TileOffsByDiagDir(d);
 
 	MakeLockTile(t, o, LOCK_MIDDLE + d, WATER_CLASS_CANAL);
-	MakeLockTile(t - delta, o, LOCK_LOWER + d, wc_lower);
-	MakeLockTile(t + delta, o, LOCK_UPPER + d, wc_upper);
+	/* Keep the current owner for the upper and lower part if it is a
+	 * water tile so we can restore the owner after deleting the lock. */
+	MakeLockTile(t - delta, IsWaterTile(t - delta) ? GetTileOwner(t - delta) : o, LOCK_LOWER + d, wc_lower);
+	MakeLockTile(t + delta, IsWaterTile(t + delta) ? GetTileOwner(t + delta) : o, LOCK_UPPER + d, wc_upper);
 }
 
 #endif /* WATER_MAP_H */