Arduino I2C implementation doesn't check for device register validity.

[SFE-Brudnerd]

There is no checking done to ensure that devReg is not nullptr. IMO this could be accomplished by adding a check above the write on line 168 like so.

if (devReg != nullptr && regLength > 0)
    _i2cPort->write(devReg, regLength);

SparkFun_Toolkit/src/sfTkArdI2C.cpp

Lines 143 to 174 in 2aa0fde

	sfTkError_t sfTkArdI2C::readRegister(uint8_t *devReg, size_t regLength, uint8_t *data, size_t numBytes,
	size_t &readBytes)
	{
	// got port
	if (!_i2cPort)
	return ksfTkErrBusNotInit;
	// Buffer valid?
	if (!data)
	return ksfTkErrBusNullBuffer;
	readBytes = 0;
	uint16_t nOrig = numBytes; // original number of bytes.
	uint8_t nChunk;
	uint16_t nReturned;
	uint16_t i; // counter in loop
	bool bFirstInter = true; // Flag for first iteration - used to send devRegister
	while (numBytes > 0)
	{
	if (bFirstInter)
	{
	_i2cPort->beginTransmission(address());
	_i2cPort->write(devReg, regLength);
	if (_i2cPort->endTransmission(stop()) != 0)
	return ksfTkErrFail; // error with the end transmission
	bFirstInter = false;
	}