[gtk+] scrolledwindow: Make sure gtk_get_current_event_state returned a state

[Timm Bäder <baedert src gnome org>]

commit 786d89cd9d8ccb275d7c48b1db73b4e067b6a90d
Author: Timm Bäder <mail baedert org>
Date:   Thu Oct 5 10:13:35 2017 +0200

    scrolledwindow: Make sure gtk_get_current_event_state returned a state
    
    Technically correct and pleases Coverity.

 gtk/gtkscrolledwindow.c |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)
---
diff --git a/gtk/gtkscrolledwindow.c b/gtk/gtkscrolledwindow.c
index 9d89da1..d73aff5 100644
--- a/gtk/gtkscrolledwindow.c
+++ b/gtk/gtkscrolledwindow.c
@@ -1314,7 +1314,9 @@ scroll_controller_scroll (GtkEventControllerScroll *scroll,
   gboolean shifted;
   GdkModifierType state;
 
-  gtk_get_current_event_state (&state);
+  if (!gtk_get_current_event_state (&state))
+    return;
+
   shifted = (state & GDK_SHIFT_MASK) != 0;
 
   priv = scrolled_window->priv;