compute checksum on unencoded buffer, not encoded buffer

Author: LeftofZen

Dat/FileParsing/SawyerStreamWriter.cs

@@ -419,7 +419,6 @@ public static MemoryStream WriteLocoObjectStream(string objName, SourceGame sour
 
 			rawObjStream.Flush();
 
-			using var encodedObjStream = new MemoryStream(Encode(encoding, rawObjStream.ToArray()));
 
 			// now obj is written, we can calculate the few bits of metadata (checksum and length) for the headers
 
@@ -441,8 +440,10 @@ public static MemoryStream WriteLocoObjectStream(string objName, SourceGame sour
 			// calculate checksum
 			var headerFlag = BitConverter.GetBytes(s5Header.Flags).AsSpan()[0..1];
 			var asciiName = objName.PadRight(8, ' ').Take(8).Select(c => (byte)c).ToArray();
-			s5Header.Checksum = SawyerStreamUtils.ComputeObjectChecksum(headerFlag, asciiName, encodedObjStream.ToArray());
+			var rawObjBytes = rawObjStream.ToArray();
+			s5Header.Checksum = SawyerStreamUtils.ComputeObjectChecksum(headerFlag, asciiName, rawObjBytes);
 
+			using var encodedObjStream = new MemoryStream(Encode(encoding, rawObjBytes));
 			var objHeader = new ObjectHeader(encoding, (uint32_t)encodedObjStream.Length);
 
 			// actual writing

Gui/ViewModels/DatTypes/S5HeaderViewModel.cs

@@ -7,7 +7,6 @@
 
 namespace OpenLoco.Gui.ViewModels
 {
-
 	[TypeConverter(typeof(ExpandableObjectConverter))]
 	public class S5HeaderViewModel : ReactiveObject
 	{