Make `ApiContainer` props return `null` if req. services unavailable

specifically `MemoryEvents` and `MemorySaveState`
now they behave like `[OptionalApi]` rather than `[RequiredApi]`

src/BizHawk.Client.Common/Api/ApiContainer.cs

@@ -9,24 +9,51 @@ namespace BizHawk.Client.Common
 	{
 		public readonly IReadOnlyDictionary<Type, IExternalApi> Libraries;
 
-		public ICommApi Comm => (ICommApi) Libraries[typeof(ICommApi)];
-		public IEmuClientApi EmuClient => (IEmuClientApi) Libraries[typeof(IEmuClientApi)];
-		public IEmulationApi Emulation => (IEmulationApi) Libraries[typeof(IEmulationApi)];
+		public ICommApi Comm
+			=> Get<ICommApi>();
+
+		public IEmuClientApi EmuClient
+			=> Get<IEmuClientApi>();
+
+		public IEmulationApi Emulation
+			=> Get<IEmulationApi>(); // requires IEmulator
 
 		[Obsolete("use Emulation")]
-		public IGameInfoApi GameInfo => (IGameInfoApi) Libraries[typeof(IGameInfoApi)];
+		public IGameInfoApi GameInfo
+			=> Get<IGameInfoApi>();
 
-		public IGuiApi Gui => (IGuiApi) Libraries[typeof(IGuiApi)];
-		public IInputApi Input => (IInputApi) Libraries[typeof(IInputApi)];
-		public IJoypadApi Joypad => (IJoypadApi) Libraries[typeof(IJoypadApi)];
-		public IMemoryApi Memory => (IMemoryApi) Libraries[typeof(IMemoryApi)];
-		public IMemoryEventsApi MemoryEvents => (IMemoryEventsApi) Libraries[typeof(IMemoryEventsApi)];
-		public IMemorySaveStateApi MemorySaveState => (IMemorySaveStateApi) Libraries[typeof(IMemorySaveStateApi)];
-		public IMovieApi Movie => (IMovieApi) Libraries[typeof(IMovieApi)];
-		public ISaveStateApi SaveState => (ISaveStateApi) Libraries[typeof(ISaveStateApi)];
-		public ISQLiteApi SQLite => (ISQLiteApi) Libraries[typeof(ISQLiteApi)];
-		public IUserDataApi UserData => (IUserDataApi) Libraries[typeof(IUserDataApi)];
-		public IToolApi Tool => (IToolApi) Libraries[typeof(IToolApi)];
+		public IGuiApi Gui
+			=> Get<IGuiApi>(); // requires IEmulator
+
+		public IInputApi Input
+			=> Get<IInputApi>();
+
+		public IJoypadApi Joypad
+			=> Get<IJoypadApi>();
+
+		public IMemoryApi Memory
+			=> Get<IMemoryApi>(); // requires IEmulator
+
+		public IMemoryEventsApi? MemoryEvents
+			=> TryGet<IMemoryEventsApi>(); // requires IDebuggable
+
+		public IMemorySaveStateApi? MemorySaveState
+			=> TryGet<IMemorySaveStateApi>(); // requires IStatable
+
+		public IMovieApi Movie
+			=> Get<IMovieApi>();
+
+		public ISaveStateApi SaveState
+			=> Get<ISaveStateApi>();
+
+		public ISQLiteApi SQLite
+			=> Get<ISQLiteApi>();
+
+		public IUserDataApi UserData
+			=> Get<IUserDataApi>();
+
+		public IToolApi Tool
+			=> Get<IToolApi>();
 
 		public ApiContainer(IReadOnlyDictionary<Type, IExternalApi> libs) => Libraries = libs;
 
@@ -34,5 +61,13 @@ namespace BizHawk.Client.Common
 		{
 			foreach (var lib in Libraries.Values) if (lib is IDisposable disposableLib) disposableLib.Dispose();
 		}
+
+		public T Get<T>()
+			where T : class, IExternalApi
+			=> (T) Libraries[typeof(T)];
+
+		public T? TryGet<T>()
+			where T : class, IExternalApi
+			=> Libraries.TryGetValue(typeof(T), out var inst) ? (T) inst : null;
 	}
 }