From 3300531083b42fac92820f4b756c9d3d945e7ab4 Mon Sep 17 00:00:00 2001
From: Even Rouault <even.rouault@spatialys.com>
Date: Tue, 9 Nov 2021 00:49:02 +0100
Subject: [PATCH] PROJStringFormatter::toString(): avoid invalid iterator
 increment (fixes #2931)

---
 src/iso19111/io.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/iso19111/io.cpp b/src/iso19111/io.cpp
index 5f2472a724..f8a4672a09 100644
--- a/src/iso19111/io.cpp
+++ b/src/iso19111/io.cpp
@@ -7678,7 +7678,7 @@ const std::string &PROJStringFormatter::toString() const {
                 iterCur = steps.erase(iterPrev, std::next(iterCur));
                 if (iterCur != steps.begin())
                     iterCur = std::prev(iterCur);
-                if (iterCur == steps.begin())
+                if (iterCur == steps.begin() && iterCur != steps.end())
                     ++iterCur;
             };