[LyX/master] XML: improve formatting of error message for unrecognised tag type.

[Thibaut Cuvelier]

commit 4f314567b6a8d87d472c3388523a3e093560b652
Author: Thibaut Cuvelier <tcuvelier at lyx.org>
Date:   Thu Dec 22 04:10:25 2022 +0100

    XML: improve formatting of error message for unrecognised tag type.
    
    Before, there was always a space after the tag, even when there were no attributes. Now, the space is output conditionally, so that the output makes more sense.
    
    Before, one space too many for the tag name (title), casting doubt on whether the code had this space hard coded or not:
    
    <!-- Output Error: Unrecognised tag type 'para' for 'title ' -->
    
    After, no such space:
    
    <!-- Output Error: Unrecognised tag type 'para' for 'title' -->
---
 src/xml.cpp |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/src/xml.cpp b/src/xml.cpp
index 7ee8d91..f466f61 100644
--- a/src/xml.cpp
+++ b/src/xml.cpp
@@ -812,7 +812,8 @@ void xml::openTag(XMLStream & xs, const docstring & tag, const docstring & attr,
 	else if (tagtype == "none")
 		xs << xml::StartTag(tag, attr);
 	else
-		xs.writeError("Unrecognised tag type '" + tagtype + "' for '" + to_utf8(tag) + " " + to_utf8(attr) + "'");
+		xs.writeError("Unrecognised tag type '" + tagtype + "' for '" + to_utf8(tag) + (attr.empty() ? "" : " ") +
+				to_utf8(attr) + "'");
 }