[LyX/2.3.x] Fix #11241, FindAdv for wedge in subscript

[Kornel Benko]

commit d63b5f548fdde340f7b241d85d7abf63a74cbbec
Author: Kornel Benko <kor...@lyx.org>
Date:   Tue Dec 11 12:12:02 2018 +0100

    Fix #11241, FindAdv for wedge in subscript
    
    Patch from ajd, completed to include also latexifyFromCursor()
---
 src/lyxfind.cpp |    9 ++++++---
 1 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/src/lyxfind.cpp b/src/lyxfind.cpp
index ddb13bf..a3a0b8b 100644
--- a/src/lyxfind.cpp
+++ b/src/lyxfind.cpp
@@ -1099,16 +1099,17 @@ docstring stringifyFromCursor(DocIterator const & cur, 
int len)
                        AS_STR_INSETS | AS_STR_SKIPDELETE | AS_STR_PLAINTEXT,
                        &runparams);
        } else if (cur.inMathed()) {
-               docstring s;
                CursorSlice cs = cur.top();
                MathData md = cs.cell();
                MathData::const_iterator it_end =
                        (( len == -1 || cs.pos() + len > int(md.size()))
                         ? md.end()
                         : md.begin() + cs.pos() + len );
+               MathData md2;
                for (MathData::const_iterator it = md.begin() + cs.pos();
                     it != it_end; ++it)
-                       s = s + asString(*it);
+                       md2.push_back(*it);
+               docstring s = asString(md2);
                LYXERR(Debug::FIND, "Stringified math: '" << s << "'");
                return s;
        }
@@ -1162,9 +1163,11 @@ docstring latexifyFromCursor(DocIterator const & cur, 
int len)
                        ((len == -1 || cs.pos() + len > int(md.size()))
                         ? md.end()
                         : md.begin() + cs.pos() + len);
+               MathData md2;
                for (MathData::const_iterator it = md.begin() + cs.pos();
                     it != it_end; ++it)
-                       ods << asString(*it);
+                       md2.push_back(*it);
+               ods << asString(md2);
 
                // Retrieve the math environment type, and add '$' or '$]'
                // or others (\end{equation}) accordingly