Gene enrichement analysis in Matlab

Hello everyone, I am trying to perform gene enrichment analysis of a set of genes. The test I have used in matlab is the hypergeometric probability density function in this Mathworks tutorial http://nl.mathworks.com/help/bioinfo/examples/exploring-microarray-gene-expression-data.html. The issue is that I noticed that some pathways had a significant p-values although they had 0 genes counted. I couldn't find a one-sided test. Thanks for your help.