Force GUI render after setting brightness

Change-Id: I4470a3a090d10f400575d45338a8349fbee8a027
diff --git a/gui/blanktimer.cpp b/gui/blanktimer.cpp
index 8333053..c8d1bcc 100644
--- a/gui/blanktimer.cpp
+++ b/gui/blanktimer.cpp
@@ -142,6 +142,7 @@
 	bstring = buff;
 	if ((TWFunc::write_file(brightness_path, bstring)) != 0)
 		return -1;
+	gui_forceRender();
 	return 0;
 }