[gtk-doc] gtkdoc-mkdb: fix warning about uninitialized var

[Stefan Kost <stefkost src gnome org>]

commit 1a468392fef5c305527f802bcb0797e10383ec67
Author: Stefan Sauer <ensonic users sf net>
Date:   Mon Dec 29 15:28:10 2014 +0100

    gtkdoc-mkdb: fix warning about uninitialized var
    
    Print source_dir if there is no dir match.

 gtkdoc-mkdb.in |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/gtkdoc-mkdb.in b/gtkdoc-mkdb.in
index f6e1eb9..62bea10 100755
--- a/gtkdoc-mkdb.in
+++ b/gtkdoc-mkdb.in
@@ -3826,7 +3826,7 @@ sub ReadSourceDocumentation {
             @TRACE@("Skipping source directory: $source_dir");
             return;
         } else {
-            @TRACE@("No match for: $1");
+            @TRACE@("No match for: ".($1 || $source_dir));
         }
     }