Field's test for linearity of the logit


I am currently working on my bachelor thesis and I ran a logistic regression on a data set I have.

From Field's 'Discovery Statistics using SPSS" I read that you should check for linearity of the logit that is (as far as I understood) derive the natural logarithm of the independent variables, then enter interaction variables and run the regression again.

Unfortunately, for some IV I have zero values in my data set which is why I can't calculate the logarithm. For this case nothing is mentioned in the book and I don't know how to proceed. Do you have any suggestions (preferably something with a source that I can rely on in my thesis)

Thanks for your help!