"Compile Error" with "Sendsms"-sample sketch

Projects Programming
7

The whole GSM class is riddled with crap like this:

GSM3ShieldV1ModemVerification.cpp

String GSM3ShieldV1ModemVerification::getIMEI()
{
	String number;
	// AT command for obtain IMEI
	String modemResponse = modemAccess.writeModemCommand("AT+GSN", 2000);
	// Parse and check response
	char res_to_compare[modemResponse.length()];
	modemResponse.toCharArray(res_to_compare, modemResponse.length());
	if(strstr(res_to_compare,"OK") == NULL)
	{	
		return NULL;

There is no excuse for using the String class at all. There is no way to convert a NULL to a String.