SDL_image: update vendored libpng from 1.6.43 to 1.6.45.

https://github.com/libsdl-org/SDL_image/commit/51307c415ab71c33c780bdb2bfab792f7f026a34

From 51307c415ab71c33c780bdb2bfab792f7f026a34 Mon Sep 17 00:00:00 2001
From: Ozkan Sezer <[EMAIL REDACTED]>
Date: Sun, 12 Jan 2025 01:24:40 +0300
Subject: [PATCH] update vendored libpng from 1.6.43 to 1.6.45.

---
 .gitmodules     | 2 +-
 external/libpng | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/.gitmodules b/.gitmodules
index 297a7d9d..a8fd3b78 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -9,7 +9,7 @@
 [submodule "external/libpng"]
 	path = external/libpng
 	url = https://github.com/libsdl-org/libpng.git
-	branch = v1.6.43-SDL
+	branch = v1.6.45-SDL
 [submodule "external/libwebp"]
 	path = external/libwebp
 	url = https://github.com/libsdl-org/libwebp.git
diff --git a/external/libpng b/external/libpng
index 1fcb3831..6ace07a4 160000
--- a/external/libpng
+++ b/external/libpng
@@ -1 +1 @@
-Subproject commit 1fcb383151fc6329ad3f82cb64fc99d2b3a0b415
+Subproject commit 6ace07a41a0a44b2d7e00a5c59770441b0646a6e