Was wondering if this was ever resolved, as i have the exact same issue on pc with version 1.5.4. here is the error text:
Message: Nullable object must have a value.
InnerException:
Stack Trace: at System.ThrowHelper.ThrowInvalidOperationException(ExceptionResource resource)
at System.Nullable`1.get_Value()
at StardewValley.Locations.VolcanoDungeon.GenerateEntities() in C:\GitlabRunner\builds\Gq5qA5P4\0\ConcernedApe\stardewvalley\Farmer\Farmer\Locations\VolcanoDungeon.cs:line 1675
at StardewValley.Locations.VolcanoDungeon.GenerateLevel(Boolean use_level_level_as_layout) in C:\GitlabRunner\builds\Gq5qA5P4\0\ConcernedApe\stardewvalley\Farmer\Farmer\Locations\VolcanoDungeon.cs:line 961
at StardewValley.Locations.VolcanoDungeon.GenerateContents(Boolean use_level_level_as_layout) in C:\GitlabRunner\builds\Gq5qA5P4\0\ConcernedApe\stardewvalley\Farmer\Farmer\Locations\VolcanoDungeon.cs:line 384
at StardewValley.Locations.VolcanoDungeon.GetLevel(String name, Boolean use_level_level_as_layout) in C:\GitlabRunner\builds\Gq5qA5P4\0\ConcernedApe\stardewvalley\Farmer\Farmer\Locations\VolcanoDungeon.cs:line 3260
at StardewValley.Game1.getLocationFromNameInLocationsList(String name, Boolean isStructure) in C:\GitlabRunner\builds\Gq5qA5P4\0\ConcernedApe\stardewvalley\Farmer\Farmer\Game1.cs:line 11679
at StardewValley.Game1.getLocationFromName(String name, Boolean isStructure) in C:\GitlabRunner\builds\Gq5qA5P4\0\ConcernedApe\stardewvalley\Farmer\Farmer\Game1.cs:line 11652
at StardewValley.Network.GameServer.warpFarmer(Farmer farmer, Int16 x, Int16 y, String name, Boolean isStructure) in C:\GitlabRunner\builds\Gq5qA5P4\0\ConcernedApe\stardewvalley\Farmer\Farmer\Network\GameServer.cs:line 689
at StardewValley.Network.GameServer.processIncomingMessage(IncomingMessage message) in C:\GitlabRunner\builds\Gq5qA5P4\0\ConcernedApe\stardewvalley\Farmer\Farmer\Network\GameServer.cs:line 705
at StardewValley.SDKs.GalaxyNetServer.onReceiveMessage(GalaxyID peer, Stream messageStream) in C:\GitlabRunner\builds\Gq5qA5P4\0\ConcernedApe\stardewvalley\Farmer\Farmer\SDKs\GalaxyNetServer.cs:line 251
at StardewValley.SDKs.GalaxySocket.Receive(Action`1 onConnection, Action`2 onMessage, Action`1 onDisconnect, Action`1 onError) in C:\GitlabRunner\builds\Gq5qA5P4\0\ConcernedApe\stardewvalley\Farmer\Farmer\SDKs\GalaxySocket.cs:line 610
at StardewValley.SDKs.GalaxyNetServer.receiveMessages() in C:\GitlabRunner\builds\Gq5qA5P4\0\ConcernedApe\stardewvalley\Farmer\Farmer\SDKs\GalaxyNetServer.cs:line 179
at StardewValley.Network.GameServer.receiveMessages() in C:\GitlabRunner\builds\Gq5qA5P4\0\ConcernedApe\stardewvalley\Farmer\Farmer\Network\GameServer.cs:line 260
at StardewValley.Multiplayer.UpdateEarly() in C:\GitlabRunner\builds\Gq5qA5P4\0\ConcernedApe\stardewvalley\Farmer\Farmer\Network\Multiplayer.cs:line 1819
at StardewValley.Game1._update(GameTime gameTime) in C:\GitlabRunner\builds\Gq5qA5P4\0\ConcernedApe\stardewvalley\Farmer\Farmer\Game1.cs:line 4162
at StardewValley.Game1.Update(GameTime gameTime) in C:\GitlabRunner\builds\Gq5qA5P4\0\ConcernedApe\stardewvalley\Farmer\Farmer\Game1.cs:line 3872
at StardewValley.GameRunner.Update(GameTime gameTime) in C:\GitlabRunner\builds\Gq5qA5P4\0\ConcernedApe\stardewvalley\Farmer\Farmer\LocalMultiplayer.cs:line 1046
at Microsoft.Xna.Framework.Game.Tick()
at Microsoft.Xna.Framework.Game.HostIdle(Object sender, EventArgs e)
at Microsoft.Xna.Framework.GameHost.OnIdle()
at Microsoft.Xna.Framework.WindowsGameHost.RunOneFrame()
at Microsoft.Xna.Framework.WindowsGameHost.ApplicationIdle(Object sender, EventArgs e)
at System.Windows.Forms.Application.ThreadContext.System.Windows.Forms.UnsafeNativeMethods.IMsoComponent.FDoIdle(Int32 grfidlef)
at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(IntPtr dwComponentID, Int32 reason, Int32 pvLoopData)
at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
at System.Windows.Forms.Application.Run(Form mainForm)
at Microsoft.Xna.Framework.WindowsGameHost.Run()
at Microsoft.Xna.Framework.Game.RunGame(Boolean useBlockingRun)
at StardewValley.Program.Main(String[] args) in C:\GitlabRunner\builds\Gq5qA5P4\0\ConcernedApe\stardewvalley\Farmer\Farmer\Program.cs:line 156