Fixed a regression when an abstract implementation has a function from a secondary base.

Signed-off-by: Dimitar Dobrev <dpldobrev@protonmail.com>

src/Generator/Generators/CSharp/CSharpSources.cs

@@ -2804,10 +2804,11 @@ namespace CppSharp.Generators.CSharp
         private string GetInstanceParam(Function function)
         {
             var from = (Class) function.Namespace;
-            var to = function.OriginalFunction == null ||
+            var to = (function.OriginalFunction == null ||
                 // we don't need to offset the instance with Itanium if there's an existing interface impl
                 (Context.ParserOptions.IsItaniumLikeAbi &&
-                 !((Class) function.OriginalNamespace).IsInterface) ?
+                 !((Class) function.OriginalNamespace).IsInterface)) &&
+                 function.SynthKind != FunctionSynthKind.AbstractImplCall ?
                 @from.BaseClass : (Class) function.OriginalFunction.Namespace;
 
             var baseOffset = 0u;

src/Generator/Passes/MultipleInheritancePass.cs

@@ -171,7 +171,8 @@ namespace CppSharp.Passes
                         ParameterTypeComparer.Instance));
                 if (existingImpl != null)
                 {
-                    existingImpl.OriginalFunction = method;
+                    if (existingImpl.OriginalFunction == null)
+                        existingImpl.OriginalFunction = method;
                     continue;
                 }
                 var impl = new Method(method)