[easytag] Tighten invariants when navigating the file list

[David King <davidk src gnome org>]

commit dc2d03daa4924aaa02ab7065ebc46b4fec9ae716
Author: David King <amigadave amigadave com>
Date:   Sat Feb 21 11:05:54 2015 +0000

    Tighten invariants when navigating the file list

 src/application_window.c |   15 +++++++--------
 1 files changed, 7 insertions(+), 8 deletions(-)
---
diff --git a/src/application_window.c b/src/application_window.c
index c35d495..163491c 100644
--- a/src/application_window.c
+++ b/src/application_window.c
@@ -1283,8 +1283,7 @@ on_go_first (GSimpleAction *action,
     self = ET_APPLICATION_WINDOW (user_data);
     priv = et_application_window_get_instance_private (self);
 
-    if (!ETCore->ETFileDisplayedList)
-        return;
+    g_return_if_fail (ETCore->ETFileDisplayedList);
 
     et_application_window_update_et_file_from_ui (self);
 
@@ -1323,8 +1322,8 @@ on_go_previous (GSimpleAction *action,
     self = ET_APPLICATION_WINDOW (user_data);
     priv = et_application_window_get_instance_private (self);
 
-    if (!ETCore->ETFileDisplayedList || !ETCore->ETFileDisplayedList->prev)
-        return;
+    g_return_if_fail (ETCore->ETFileDisplayedList
+                      && ETCore->ETFileDisplayedList->prev);
 
     et_application_window_update_et_file_from_ui (self);
 
@@ -1362,8 +1361,8 @@ on_go_next (GSimpleAction *action,
     self = ET_APPLICATION_WINDOW (user_data);
     priv = et_application_window_get_instance_private (self);
 
-    if (!ETCore->ETFileDisplayedList || !ETCore->ETFileDisplayedList->next)
-        return;
+    g_return_if_fail (ETCore->ETFileDisplayedList
+                      && ETCore->ETFileDisplayedList->next);
 
     et_application_window_update_et_file_from_ui (self);
 
@@ -1401,8 +1400,8 @@ on_go_last (GSimpleAction *action,
     self = ET_APPLICATION_WINDOW (user_data);
     priv = et_application_window_get_instance_private (self);
 
-    if (!ETCore->ETFileDisplayedList || !ETCore->ETFileDisplayedList->next)
-        return;
+    g_return_if_fail (ETCore->ETFileDisplayedList
+                      && ETCore->ETFileDisplayedList->next);
 
     et_application_window_update_et_file_from_ui (self);