MLEM may cause extreme values on recon

## Code to reproduce the problem (If applicable)
geo=defaultGeometry('nVoxel',[128;128;128]);

angles=linspace(0,2*pi,100);
head=headPhantom(geo.nVoxel);

projections=Ax(head,geo,angles,'interpolated')
noise_projections=addCTnoise(projections);

imgMLEM=MLEM(noise_projections,geo,angles,20)

plotImg(imgMLEM,'Dim','Z')

## Specifications

When the MLEM algorithm is used to reconstruct the noise_projections ,the image cannot be reconstructed and is completely black.
the image can be reconstructed by the projections.

- MATLAB version: R2021a
- OS:
- CUDA version: 11.04