Fixed a possible crash when getting a declaration from a type.

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

src/AST/TypeExtensions.cs

@@ -148,7 +148,7 @@
                     if (templateTemplateParameter != null)
                         return (decl = templateTemplateParameter.TemplatedDecl as T) != null;
                 }
-                tagType = (TagType) (type.Desugared.Type.GetFinalPointee() ?? type.Desugared.Type);
+                tagType = (type.Desugared.Type.GetFinalPointee() ?? type.Desugared.Type) as TagType;
             }
             else
             {