SDL_image: png: fix -Wclobber warning

From 98e73b8fd3c266cfbf224f02ee4b27918edf522e Mon Sep 17 00:00:00 2001
From: Anonymous Maarten <[EMAIL REDACTED]>
Date: Sun, 18 Jun 2023 12:30:06 +0200
Subject: [PATCH] png: fix -Wclobber warning

Co-authored-by: Ozkan Sezer <sezeroz@gmail.com>
---
 src/IMG_png.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/src/IMG_png.c b/src/IMG_png.c
index 589fa523..c8ba8635 100644
--- a/src/IMG_png.c
+++ b/src/IMG_png.c
@@ -242,11 +242,11 @@ SDL_Surface *IMG_LoadPNG_RW(SDL_RWops *src)
     png_infop info_ptr;
     png_uint_32 width, height;
     int bit_depth, color_type, interlace_type, num_channels;
-    Uint32 format = SDL_PIXELFORMAT_UNKNOWN;
+    Uint32 format;
     SDL_Palette *palette;
     png_bytep *row_pointers;
     int row, i;
-    int ckey = -1;
+    int ckey;
     png_color_16 *transv;
 
     if ( !src ) {
@@ -323,6 +323,7 @@ SDL_Surface *IMG_LoadPNG_RW(SDL_RWops *src)
     /* For images with a single "transparent colour", set colour key;
        if more than one index has transparency, or if partially transparent
        entries exist, use full alpha channel */
+    ckey = -1;
     if (lib.png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS)) {
         int num_trans;
         Uint8 *trans;
@@ -362,7 +363,8 @@ SDL_Surface *IMG_LoadPNG_RW(SDL_RWops *src)
 
     /* Allocate the SDL surface to hold the image */
     num_channels = lib.png_get_channels(png_ptr, info_ptr);
-   
+
+    format = SDL_PIXELFORMAT_UNKNOWN;
     if (num_channels == 3) {
        format = SDL_PIXELFORMAT_RGB24;
     } else if (num_channels == 4) {