[vala/0.14] girparser: Fix criticals on calculate_common_prefix

[JÃrg Billeter <juergbi src gnome org>]

commit 3a204144893cb5b0a33cd2025d5f485ea317dc71
Author: Luca Bruno <lucabru src gnome org>
Date:   Fri Dec 9 11:02:10 2011 +0100

    girparser: Fix criticals on calculate_common_prefix

 vala/valagirparser.vala |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/vala/valagirparser.vala b/vala/valagirparser.vala
index 1908a05..6152841 100644
--- a/vala/valagirparser.vala
+++ b/vala/valagirparser.vala
@@ -1932,7 +1932,7 @@ public class Vala.GirParser : CodeVisitor {
 		end_element ("alias");
 	}
 
-	private void calculate_common_prefix (ref string common_prefix, string cname) {
+	private void calculate_common_prefix (ref string? common_prefix, string cname) {
 		if (common_prefix == null) {
 			common_prefix = cname;
 			while (common_prefix.length > 0 && !common_prefix.has_suffix ("_")) {