odd number selection bug

[rayary]

Came upon this code through google search

https://github.com/karimhamdanali/codility/blob/6ddaf5e714feb48b051838379d7a659775450e19/src/codility/OddOccurrencesInArray.java#L41-L46

If the input array is arranged so that the odd number occurs before the pairs, the output will be the last number did not exist in the set, which may not necessarily be the odd number. for example, {7, 9, 3, 9, 3, 9, 9} will return 3