tex2lyx: do not force default bibliography style if none is set

Some classes provide a \bibliographystyle, so we must not output any
\bibliographystyle if none is set in the TeX file.

Fixes: #10673
(cherry picked from commit ed331bedd6)

src/tex2lyx/text.cpp

@@ -2473,7 +2473,9 @@ void parse_text(Parser & p, ostream & os, unsigned flags, bool outer,
 	// nocite{*} option (needed for bibtex inset)
 	string btprint;
 	string contentslineContent;
-	string bibliographystyle = "default";
+	// Some classes provide a \bibliographystyle, so do not output
+	// any if none is explicitly set.
+	string bibliographystyle;
 	bool const use_natbib = isProvided("natbib");
 	bool const use_jurabib = isProvided("jurabib");
 	string last_env;

status.23x

@@ -74,6 +74,8 @@ What's new
 
 * TEX2LYX
 
+- Do not force default bibliography style if none is set (bug 10673).
+
 
 * ADVANCED FIND AND REPLACE