[AI] Navmesh tiles are fully removed when a tile containing an automatic navlink is regenerated using Dynamic Modifiers Only generation

An unusual interaction has been found when using automatic navlink generation combined with Dynamic Modifiers Only navmesh generation. When an nav area is modified in a tile that contains an automatic navlink, the entire navmesh tile is removed rather than having the tile update the nav areas. Everything works as expected in static and fully dynamic modes.