[nautilus] Fix build in Clang

[Carlos Soriano <csoriano src gnome org>]

commit 6114cb85855406a8cb0f339f5b0cfffca5789d95
Author: Albert Vaca Cintora <albertvaka gmail com>
Date:   Mon Mar 18 00:46:15 2019 +0100

    Fix build in Clang
    
    I was getting:
    error: variable 'string' is used uninitialized whenever 'if' condition is
    false [-Werror,-Wsometimes-uninitialized]

 extensions/audio-video-properties/totem-properties-view.c | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/extensions/audio-video-properties/totem-properties-view.c 
b/extensions/audio-video-properties/totem-properties-view.c
index af50be060..f280fa2c5 100644
--- a/extensions/audio-video-properties/totem-properties-view.c
+++ b/extensions/audio-video-properties/totem-properties-view.c
@@ -232,6 +232,8 @@ update_audio (TotemPropertiesView    *props,
                        string = g_strdup (_("Mono"));
                } else if (channels == 2) {
                        string = g_strdup (_("Stereo"));
+               } else {
+                       string = g_strdup (""); //Should not happen
                }
                bacon_video_widget_properties_set_label (props->priv->props,
                                                         "channels",