[GaussianNoiseModel] Crash if initialized with zero bias standard deviation

[oysstu]

The bias state is sampled when loading sdf::Noise. If the bias standard deviation is set to zero, the program exits. I can see legitimate use for a deterministic bias state (or disabling the bias state altogether).

gz-sensors/src/GaussianNoiseModel.cc

Lines 88 to 90 in e52f97c

	biasMean = _sdf.BiasMean();
	biasStdDev = _sdf.BiasStdDev();
	this->dataPtr->bias = math::Rand::DblNormal(biasMean, biasStdDev);

The program also crashes when sampling the distribution if the state standard deviation is zero. Usually that would indicate wrong parameters being passed, but I suppose a legitimate use case could be to disable noise altogether.

gz-sensors/src/GaussianNoiseModel.cc

Lines 111 to 112 in e52f97c

	double whiteNoise = math::Rand::DblNormal(
	this->dataPtr->mean, this->dataPtr->stdDev);