Mirrored geometry won't combine.

Hello,

Can anybody help me to merge the mirrored bodies. I have tried merge feature within mirror function and combine feature but I'm unsuccessful in both cases. The errors I get are:

1) Failed to merge the newly generated body with the work piece (in mirror feature)

2) Unable to create this feature because it would result in zero-thickness geometry (in combine feature after mirroring without ticking merge solids)

I have attached the file here so if you could help I would really appreciate!

SolidworksParts And Features