Removed [CoreConstructor("ZXSpectrum")] identifier (as this was causing an exception when loading roms for other systems

BizHawk.Emulation.Common/SystemLookup.cs

@@ -32,7 +32,8 @@ namespace BizHawk.Emulation.Common
 
 			new SystemInfo { SystemId = "C64", FullName = "Commodore 64" },
 			new SystemInfo { SystemId = "AppleII", FullName = "Apple II" },
-			new SystemInfo { SystemId = "INTV", FullName = "Intellivision" }
+			new SystemInfo { SystemId = "INTV", FullName = "Intellivision" },
+            new SystemInfo { SystemId = "ZXSpectrum", FullName = "Sinclair ZX Spectrum" }
 		};
 
 		public SystemInfo this[string systemId]

BizHawk.Emulation.Cores/Computers/SinclairSpectrum/ZXSpectrum.IEmulator.cs

@@ -41,7 +41,16 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
             }
         }
 
-        public int Frame => _machine.FrameCount;
+        public int Frame
+        {
+            get
+            {
+                if (_machine == null)
+                    return 0;
+                else
+                    return _machine.FrameCount;
+            }
+        }
 
         public string SystemId => "ZXSpectrum";
 

BizHawk.Emulation.Cores/Computers/SinclairSpectrum/ZXSpectrum.cs

@@ -18,7 +18,6 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
     [ServiceNotApplicable(typeof(IDriveLight))]
     public partial class ZXSpectrum : IDebuggable, IInputPollable, IStatable, IRegionable
     {
-        [CoreConstructor("ZXSpectrum")]
         public ZXSpectrum(CoreComm comm, IEnumerable<byte[]> files, List<GameInfo> game, object settings, object syncSettings)
         {            
             var ser = new BasicServiceProvider(this);

BizHawk.Emulation.Cores/FileID.cs

@@ -42,6 +42,7 @@ namespace BizHawk.Emulation.Cores
 		WS, WSC, NGC,
 
 		C64, 
+        ZXSpectrum,
 		INT,
 		A26, A52, A78, LNX,