Cast user pref strings. (#6123)

src/main.cpp

@@ -117,7 +117,7 @@ AudioThread *audioThread = nullptr;
 
 using namespace concurrency;
 
-volatile static const char slipstreamTZString[] = USERPREFS_TZ_STRING;
+volatile static const char slipstreamTZString[] = {USERPREFS_TZ_STRING};
 
 // We always create a screen object, but we only init it if we find the hardware
 graphics::Screen *screen = nullptr;