Prevent out-of-bounds array access

Fixes https://github.com/itgmania/itgmania/issues/27

src/archutils/Darwin/KeyboardDevice.cpp

@@ -482,7 +482,14 @@ bool KeyboardDevice::DeviceButtonToMacVirtualKey( DeviceButton button, UInt8 &iM
 		}
 		bInited = true;
 	}
+	if (button < sizeof(g_iDeviceButtonToMacVirtualKey))
+	{
 		iMacVKOut = g_iDeviceButtonToMacVirtualKey[button];
+	}
+	else
+	{
+		iMacVKOut = 0xFF;
+	}
 	return iMacVKOut != 0xFF;
 }