[LyX/master] Fix ticket #13345: bad use of iterators

[Koji Yokota]

commit 13b05603d21a05cf70f4327b61ed6a65cac2bffb
Author: Koji Yokota <yokota at lyx.org>
Date:   Tue Jun 30 19:09:41 2026 +0900

    Fix ticket #13345: bad use of iterators
---
 src/frontends/qt/GuiInputMethod.cpp | 5 ++++-
 src/frontends/qt/GuiInputMethod.h   | 7 +++++++
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/src/frontends/qt/GuiInputMethod.cpp b/src/frontends/qt/GuiInputMethod.cpp
index 9f1d050967..86b1424202 100644
--- a/src/frontends/qt/GuiInputMethod.cpp
+++ b/src/frontends/qt/GuiInputMethod.cpp
@@ -736,7 +736,10 @@ pos_type GuiInputMethod::pickNextSegFromTurnout(pos_type next_seg_pos, size_type
 				LYXERR(Debug::KEY, "Removing from preedit turnout: ["
 				        << it->start_ << ", "
 				        << it->start_ + it->length_ << ")");
-				d->seg_turnout_.erase(it);
+				for (auto it2 = d->seg_turnout_.begin();
+				     it2 != d->seg_turnout_.end(); it2++)
+					if (*it == *it2)
+						d->seg_turnout_.erase(it2);
 			}
 		}
 	}
diff --git a/src/frontends/qt/GuiInputMethod.h b/src/frontends/qt/GuiInputMethod.h
index 9945b7f4b5..36b129f63f 100644
--- a/src/frontends/qt/GuiInputMethod.h
+++ b/src/frontends/qt/GuiInputMethod.h
@@ -45,6 +45,13 @@ public:
 		bool operator<(const PreeditSegment & another) const {
 			return start_ < another.start_;
 		}
+		bool operator>(const PreeditSegment & another) const {
+			return start_ > another.start_;
+		}
+		bool operator==(const PreeditSegment & another) const {
+			return start_ == another.start_ && length_ == another.length_ &&
+			        char_format_ == another.char_format_;
+		}
 	};
 
 	struct PreeditStyle {