Fix check of webmail.inc file

bin/v-change-sys-webmail

@@ -44,7 +44,9 @@ done
 if [ "$WEB_SYSTEM" = 'apache2' ]; then
     sed -i "s|Alias \/$OLD_ALIAS|Alias \/$NEW_ALIAS|gI" /etc/apache2/conf.d/roundcube.conf
 fi
-sed -i "s|location \/$OLD_ALIAS|location \/$NEW_ALIAS|gI" /etc/nginx/conf.d/webmail.inc
+if [ -e /etc/nginx/conf.d/webmail.inc ]; then
+    sed -i "s|location \/$OLD_ALIAS|location \/$NEW_ALIAS|gI" /etc/nginx/conf.d/webmail.inc
+fi
 
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