You should replace the newline character with an empty string of space. Since there's no string replace operator in eZP you'll have to use some extension that allows you to do it. For example wrap operator, which allows you to execute any PHP function. Or you can search on projects.ez.no for an extension that implements the string replace operator.
To eZ team: it's a real shame that eZP by default lacks such basic and essential operators for string manipulation.
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Nothing is impossible. Not if you can imagine it!