Support null indices when the index is 32 bits

LibCpp2IL/Metadata/Il2CppMetadata.cs

@@ -171,7 +171,7 @@
         return new Il2CppMetadata(new MemoryStream(bytes), unityVersion, actualVersion);
     }
 
     private Il2CppMetadata(MemoryStream stream, UnityVersion unityVersion, float metadataVersion) : base(stream)
     {
         UnityVersion = unityVersion;
         MetadataVersion = metadataVersion;
@@ -420,7 +420,8 @@
             foreach (var il2CppFieldDefaultValue in fieldDefaultValues)
             {
                 _fieldDefaultValueLookup[il2CppFieldDefaultValue.fieldIndex] = il2CppFieldDefaultValue;
-                _fieldDefaultLookupNew[GetFieldDefinitionFromIndex(il2CppFieldDefaultValue.fieldIndex)] = il2CppFieldDefaultValue;
+                if (il2CppFieldDefaultValue.fieldIndex.IsNonNull)
+                    _fieldDefaultLookupNew[GetFieldDefinitionFromIndex(il2CppFieldDefaultValue.fieldIndex)] = il2CppFieldDefaultValue;
             }
 
             LibLogger.VerboseNewline($"OK ({(DateTime.Now - start).TotalMilliseconds} ms)");

LibCpp2IL/Metadata/Il2CppVariableWidthIndex.cs

@@ -71,7 +71,10 @@ public static Il2CppVariableWidthIndex<T> Read(ClassReadingBinaryReader reader)
                     return Null;
                 return new(val2);
             case 4:
-                return new(reader.ReadInt32());
+                var val3 = reader.ReadInt32();
+                if (val3 == int.MaxValue)
+                    return Null;
+                return new(val3);
             default:
                 throw new Exception($"Invalid width {widthForThisTypeOnCurrentApplication} for Il2CppVariableWidthIndex of type {typeof(T)}.");
         }