[LyX/master] Do not output label tags if there is no label

[Richard Kimberly Heck]

commit b37ac5807f388a690436e4af809acf6506905eb5
Author: Richard Kimberly Heck <rikiheck at lyx.org>
Date:   Sun Dec 4 12:01:42 2022 -0500

    Do not output label tags if there is no label
---
 src/output_xhtml.cpp |   11 +++++++----
 1 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/src/output_xhtml.cpp b/src/output_xhtml.cpp
index 9924be1..47c4145 100644
--- a/src/output_xhtml.cpp
+++ b/src/output_xhtml.cpp
@@ -466,10 +466,13 @@ ParagraphList::const_iterator makeEnvironment(Buffer const & buf,
 							xs << xml::CR();
 						}
 						else {
-							openLabelTag(xs, style);
-							xs << par->params().labelString();
-							closeLabelTag(xs, style);
-							xs << xml::CR();
+							docstring const & ls = par->params().labelString();
+							if (!ls.empty()) {
+								openLabelTag(xs, style);
+								xs << ls;
+								closeLabelTag(xs, style);
+								xs << xml::CR();
+							}
 						}
 					}
 				} // end label output