[gnome-builder] gca: check for valid language before getting id

[Christian Hergert <chergert src gnome org>]

commit 8acc9ff4b6681c4fcabbbe266d19914d114ec3be
Author: Christian Hergert <chergert redhat com>
Date:   Tue Jul 19 18:21:03 2016 -0700

    gca: check for valid language before getting id
    
    Fixes a CRITICAL warning for calling gtk_source_language_get_id() with a
    NULL GtkSourceLanguage.

 .../ide-gca-diagnostic-provider.c                  |    8 +++++---
 1 files changed, 5 insertions(+), 3 deletions(-)
---
diff --git a/plugins/gnome-code-assistance/ide-gca-diagnostic-provider.c 
b/plugins/gnome-code-assistance/ide-gca-diagnostic-provider.c
index c2d4b67..ff36e9b 100644
--- a/plugins/gnome-code-assistance/ide-gca-diagnostic-provider.c
+++ b/plugins/gnome-code-assistance/ide-gca-diagnostic-provider.c
@@ -415,7 +415,7 @@ ide_gca_diagnostic_provider_diagnose_async (IdeDiagnosticProvider *provider,
   GtkSourceLanguage *language;
   IdeContext *context;
   IdeUnsavedFiles *files;
-  const gchar *language_id;
+  const gchar *language_id = NULL;
   GFile *gfile;
 
   IDE_ENTRY;
@@ -425,9 +425,11 @@ ide_gca_diagnostic_provider_diagnose_async (IdeDiagnosticProvider *provider,
   task = g_task_new (self, cancellable, callback, user_data);
 
   language = ide_file_get_language (file);
-  language_id = gtk_source_language_get_id (language);
 
-  if (!language_id)
+  if (language != NULL)
+    language_id = gtk_source_language_get_id (language);
+
+  if (language_id == NULL)
     {
       g_task_return_new_error (task,
                                G_IO_ERROR,