Added a check for 'null' before getting the native pointer of a wrapped object.

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

src/Generator/Generators/CSharp/CSharpMarshal.cs

@@ -572,17 +572,24 @@ namespace CppSharp.Generators.CSharp
                 return;
             }
 
-            if (Context.Parameter.Type.IsAddress())
+            string param = Helpers.SafeIdentifier(Context.Parameter.Name);
+            Type type = Context.Parameter.Type.Desugar();
+            if (type.IsAddress())
             {
-                Context.Return.Write("{0}.{1}", Helpers.SafeIdentifier(Context.Parameter.Name),
-                    Helpers.InstanceIdentifier);
+                Class decl;
+                if (type.IsTagDecl(out decl) && decl.IsValueType)
+                    Context.Return.Write("{0}.{1}", param, Helpers.InstanceIdentifier);
+                else
+                    Context.Return.Write("{0} == ({2}) null ? global::System.IntPtr.Zero : {0}.{1}", param,
+                        Helpers.InstanceIdentifier, type);
                 return;
             }
 
             var qualifiedIdentifier = CSharpMarshalNativeToManagedPrinter.QualifiedIdentifier(
                 @class.OriginalClass ?? @class);
-            Context.Return.Write("*({0}.Internal*){1}.{2}", qualifiedIdentifier,
-                Helpers.SafeIdentifier(Context.Parameter.Name), Helpers.InstanceIdentifier);
+            Context.Return.Write(
+                "{1} == ({0}) null ? new {0}.Internal() : *({0}.Internal*) ({1}.{2})", qualifiedIdentifier,
+                param, Helpers.InstanceIdentifier);
         }
 
         private void MarshalValueClass(Class @class)

tests/CSharpTemp/CSharpTemp.Tests.cs

@@ -33,7 +33,7 @@ public class CSharpTempTests
     [Test]
     public void TestFixedArrays()
     {
-        Qux qux = new Qux();
+        Qux qux = new Qux(null);
         var array = new[] { 1, 2, 3 };
         qux.Array = array;
         for (int i = 0; i < qux.Array.Length; i++)

tests/CSharpTemp/CSharpTemp.cpp

@@ -31,6 +31,16 @@ const Foo& Bar::operator[](int i) const
     return m_foo;
 }
 
+Qux::Qux()
+{
+
+}
+
+Qux::Qux(Foo foo)
+{
+
+}
+
 int Qux::farAwayFunc() const
 {
     return 20;

tests/CSharpTemp/CSharpTemp.h

@@ -21,6 +21,8 @@ protected:
 class DLL_API Qux
 {
 public:
+    Qux();
+    Qux(Foo foo);
     int farAwayFunc() const;
     int array[3];
 };