Roboto Slab Problem

Hi,
In my blog I use google fonts Roboto slab (from theme dashboard configuration, no css modified), but I get a bad request from google.
The called link is
https://fonts.googleapis.com/css?family=Roboto\2bSlab\3a100,300,regular,700
From google template i get correct link, that is
https://fonts.googleapis.com/css?family=Roboto+Slab

How I can correct the link into theme ?

Thanks

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