Don’t worry – the mixture is food safe, is not harmful in any way and the freeze pack will still cool your drinks.
If you can identify the leak, you have two options:
1) Seal the hole with a flexible, low temperature sealant like Loctite Stick and Seal or E6000
OR
2) Squeeze out the rest of the gel from that cell and dispose of in the trash
Remember – even missing one cell, your phase change freeze pack will still work and cool your drinks to make them refreshingly frosty!