[vala] Set gir_shared_library argument to be null by default, avoid breaking API

[Luca Bruno <lucabru src gnome org>]

commit df74eea32ef83c805c2503bcec60c5e3473736b3
Author: Luca Bruno <lucabru src gnome org>
Date:   Tue Aug 11 12:07:47 2015 +0200

    Set gir_shared_library argument to be null by default, avoid breaking API

 codegen/valagirwriter.vala |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/codegen/valagirwriter.vala b/codegen/valagirwriter.vala
index 3a70e68..eff03ca 100644
--- a/codegen/valagirwriter.vala
+++ b/codegen/valagirwriter.vala
@@ -142,7 +142,7 @@ public class Vala.GIRWriter : CodeVisitor {
         * @param context  a code context
         * @param filename a relative or absolute filename
         */
-       public void write_file (CodeContext context, string directory, string gir_filename, string 
gir_namespace, string gir_version, string package, string? gir_shared_library) {
+       public void write_file (CodeContext context, string directory, string gir_filename, string 
gir_namespace, string gir_version, string package, string? gir_shared_library = null) {
                this.context = context;
                this.directory = directory;
                this.gir_namespace = gir_namespace;