The order of the if else logic seems to have been reversed. Depending on the values of _emissionRate.unwrap() and _emissionRate involved, this could be crucial enough to make the function truncate to zero when _emissionRate was more than one (1e18) and used as the divisor. On the other hand, the function could also overflow when _emissionRate was less than one and used as the divisor. If thats the case, I suggest removing the if clause and keep only the else clause (with one of the parentheses removed) that will cater to both circumstances.
https://github.com/GenerationSoftware/pt-v5-cgda-liquidator/blob/7f95bcacd4a566c2becb98d55c1886cadbaa8897/src/libraries/ContinuousGDA.sol#L38-L42
