Fixed compile error

Author: JordanL8

src/Generator/Generators/CSharp/CSharpSources.cs

@@ -2485,7 +2485,7 @@ private void GenerateNativeConstructor(Class @class)
 internal static{(@new ? " new" : string.Empty)} {printedClass} __GetInstance({TypePrinter.IntPtrType} native)
 {{
     if (singletonInstance != null)
-        return singletonInstance
+        return singletonInstance;
     if (!{Helpers.TryGetNativeToManagedMappingIdentifier}(native, out var managed))
         throw new global::System.Exception(""No managed instance was found"");
     var result = ({printedClass})managed;