Hi Abdallah,
You have encountered a bug we experienced with the last release of OptiSystem. It is now fixed and the release will be out hopefully mid January.
A work around is not to convert noise bins in the EDFA, but to convert it later with the component found in “Signal Processing Library/Tools/Optical library” named “Convert to Sampled Signals”.
Sorry for the inconvenience and let me know if it works out for you.