A phantom linebreak with Polyglossia and BibLaTeX

Edit: it is a problem with BibLaTeX. The good news is that there appears to be a fix coming soon—and you can add it to your preamble now. Thanks, Ulrike Fischer for the pointer.

A picture is worth a thousand words. If you check the screenshot below you will see that there is a strange linebreak right after an opening parenthesis. This phantom linebreak happens the first time I use textgreek to enter ancient Greek text. This unwanted linebreak never appears again. (You can see that from the image and MWE: I include the exact same sentence later in the paragraph, but there is no phantom linebreak the second time.) I cannot figure out exactly what causes the linebreak, but I think I’ve narrowed it down to an interaction (?) Polyglossia and Windy City.

My MWE is below. After adding and removing things, the problem seems to be Polyglossia and Windy City. If I remove Windy City, the problem goes away. If I swap Babel for Polyglossia, the problem goes away. But I don’t want to remove either Windy City or Polyglossia if I can avoid it. If it’s a bug on one side or the other, I am happy to file a bug report, but I am not sure where to start looking.

documentclass[12pt,letterpaper]{article}

usepackage[no-math]{fontspec}
setmainfont{Baskerville}

usepackage[nolocalmarks]{polyglossia}
setdefaultlanguage{english}
setotherlanguage[variant=classic]{latin}
setotherlanguage[variant=ancient]{greek}
newfontfamilygreekfont[Script=Greek,Scale=MatchLowercase]{GFS Neohellenic}

usepackage{parskip}
usepackage{csquotes}
usepackage[style=windycity,backend=biber]{biblatex}
addbibresource{plato.bib}

begin{document}

section*{Socratic Irony}

Kreuz cites Aristotle for testimony about Socratic irony.
Aristotle mentions Socrates in Book 4 of textit{Nichomachean Ethics} while he is discussing the virtue concerning truthfulness about one's abilities.
This (unnamed) virtue, says Aristotle in textit{NE} 4.7, is a mean between boasting and false modesty (textgreek{ἀλαζονεία} and textgreek{εἰρωνεία}).
Boasters claim admirable qualities that they lack or they exaggerate their share in those qualities; the textit{eiron} disavows admirable qualities that they possess.
In this context, Aristotle says, ``The qualities that win reputation are the ones that these people especially disavow, as Socrates also used to do'' (textit{NE} 4.7 in Irwin's translation).
This (unnamed) virtue, says Aristotle in textit{NE} 4.7, is a mean between boasting and false modesty (textgreek{ἀλαζονεία} and textgreek{εἰρωνεία}).

end{document}