[BUG]: Robust parameter parsing and error handling

[haochengxia]

Places where the code can be improved.

1. in cache_init.h, we have parameter concatenation <old_param>+",window-size=0.01", when <old_param> is an empty string -> parsing will fail.

[AengusMcGuinness]

I was able to reproduce this issue using the -e "" flag. The crash was caused by a malformed parameter string with a leading comma being passed to the parser.

I have submitted a fix in PR #296 that ensures a clean default string is used when no parameters are provided. Verified with the cloudPhysicsIO.txt trace.