[gnome-builder] gettext: ensure lang_id is initialized

[Christian Hergert <chergert src gnome org>]

commit c8fae4b5f4e0c8b9c4cdf1ccfb691800a2caa229
Author: Christian Hergert <chergert redhat com>
Date:   Sun Jan 14 01:51:38 2018 -0800

    gettext: ensure lang_id is initialized
    
    And don't pass NULL to the string formatter.

 src/plugins/gettext/ide-gettext-diagnostic-provider.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/src/plugins/gettext/ide-gettext-diagnostic-provider.c 
b/src/plugins/gettext/ide-gettext-diagnostic-provider.c
index ff4f5968d..6fa75db20 100644
--- a/src/plugins/gettext/ide-gettext-diagnostic-provider.c
+++ b/src/plugins/gettext/ide-gettext-diagnostic-provider.c
@@ -155,7 +155,7 @@ ide_gettext_diagnostic_provider_diagnose_async (IdeDiagnosticProvider *provider,
   g_autoptr(GTask) task = NULL;
   g_autoptr(GError) error = NULL;
   GtkSourceLanguage *language;
-  const gchar *lang_id;
+  const gchar *lang_id = NULL;
   const gchar *xgettext_id;
 
   g_assert (IDE_IS_GETTEXT_DIAGNOSTIC_PROVIDER (self));
@@ -177,7 +177,7 @@ ide_gettext_diagnostic_provider_diagnose_async (IdeDiagnosticProvider *provider,
                                G_IO_ERROR,
                                G_IO_ERROR_NOT_SUPPORTED,
                                "Language %s is not supported",
-                               lang_id);
+                               lang_id ?: "plain-text");
       return;
     }