Many patient registration form allows patient to be created w/o Gender being specified. Please check on patient list load if gender of patient is available or not. Set Gender: "---" if undefined
Please check attachment for clarification of bug.
another OPD bug - can you take a look at this one too? Basically, if you create a patient without a "male" or "female" gender, then the UI doesn't handle this properly in the OPD module