[mutter] core: Fix compiler warning

[Jonas Ådahl <jadahl src gnome org>]

commit 562cf142584117481260aaa5c6f2c3e93fb84229
Author: Olivier Fourdan <ofourdan redhat com>
Date:   Wed Jan 23 09:29:39 2019 +0100

    core: Fix compiler warning
    
    Fix compiler warning: ‘startup_id’ may be used uninitialized in
    `meta_launch_context_get_startup_notify_id()`.
    
    Also change `gchar` to plain `char` while at it.
    
    https://gitlab.gnome.org/GNOME/mutter/merge_requests/406

 src/core/meta-launch-context.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/src/core/meta-launch-context.c b/src/core/meta-launch-context.c
index d70f5a5e7..eb8671bb2 100644
--- a/src/core/meta-launch-context.c
+++ b/src/core/meta-launch-context.c
@@ -127,7 +127,7 @@ meta_launch_context_get_startup_notify_id (GAppLaunchContext *launch_context,
   MetaLaunchContext *context = META_LAUNCH_CONTEXT (launch_context);
   MetaDisplay *display = context->display;
   int workspace_idx = -1;
-  gchar *startup_id;
+  char *startup_id = NULL;
 
   if (context->workspace)
     workspace_idx = meta_workspace_index (context->workspace);
@@ -148,7 +148,7 @@ meta_launch_context_get_startup_notify_id (GAppLaunchContext *launch_context,
 
   if (!startup_id)
     {
-      const gchar *application_id = NULL;
+      const char *application_id = NULL;
       MetaStartupNotification *sn;
       MetaStartupSequence *seq;