tex2lyx: reset language after polyglossia lang environment has been closed

Fixes #11878

(cherry picked from commit 5b2479176b)

src/tex2lyx/text.cpp

@@ -1641,11 +1641,15 @@ void parse_environment(Parser & p, ostream & os, bool outer,
 			parent_context.check_end_layout(os);
 			parent_context.new_paragraph(os);
 		}
+		// store previous language because we must reset it at the end
+		string const lang_old = parent_context.font.language;
 		// save the language in the context so that it is
 		// handled by parse_text
 		parent_context.font.language =
 			preamble.polyglossia2lyx(fromPolyglossiaEnvironment(name));
 		parse_text(p, os, FLAG_END, outer, parent_context);
+		// reset previous language
+		parent_context.font.language = lang_old;
 		// Just in case the environment is empty
 		parent_context.extra_stuff.erase();
 		// We must begin a new paragraph to reset the language

status.23x

@@ -155,6 +155,8 @@ What's new
 
 * TEX2LYX
 
+- Fix import of nested polyglossia language environments (bug 11878).
+
 
 * LYXHTML