core(fonts): fix infinite loop

[patrickhulce]

partial fix to address #4486 and prevent an infinite loop when getting an exception

[wardpeet]

not sure that's the cause of infinite loop but LGTM :)

[patrickhulce]

not sure that's the cause of infinite loop but LGTM :)

it certainly was in my case :)

getFontFaceFromStylesheets calls loadStylesheetWithCORS on all errors, loadStylesheetWithCORS calls getFontFaceFromStylesheets and so the cycle repeats infinitely if the error isn't solved by CORS fetching