Root menu: prevent infinite loop trying to exit plugin

Rockbox could enter into an infinite loop when last_screen
and next_screen were both GO_TO_PREVIOUS, which
happened when trying to quit PictureFlow in the following
scenario:

1) start playback from PictureFlow plugin
2) return (or be returned) to WPS directly
3) wait for playback to finish and to be returned to PF
plugin

Change-Id: I0b52d4df56d416f81cef027d9024e964a734fcdc

1 files changed, 2 insertions, 0 deletions

diff --git a/apps/root_menu.c b/apps/root_menu.c
index e4020ae6c7..c10064499c 100644
--- a/apps/root_menu.c
+++ b/apps/root_menu.c
@@ -898,6 +898,8 @@ void root_menu(void)
                 next_screen = last_screen;
                 if (last_screen == GO_TO_PLUGIN)/* for WPS */
                     last_screen = GO_TO_PREVIOUS;
+                else if (last_screen == GO_TO_PREVIOUS)
+                    next_screen = GO_TO_ROOT;
                 break;
             }