sdl12-compat: warning fixes after PR41 merge.

SDL Commits
1 
From 710125fb63ec660ec4b0f8c2eb1053ad006b2b20 Mon Sep 17 00:00:00 2001
From: Ozkan Sezer <[EMAIL REDACTED]>
Date: Mon, 12 Apr 2021 12:28:02 +0300
Subject: [PATCH] warning fixes after PR41 merge.

---
 src/SDL12_compat.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/SDL12_compat.c b/src/SDL12_compat.c
index 6767d27..c4b0830 100644
--- a/src/SDL12_compat.c
+++ b/src/SDL12_compat.c
@@ -2310,8 +2310,8 @@ EventFilter20to12(void *data, SDL_Event *event20)
         case SDL_TEXTINPUT:
         {
             char *text = event20->text.text;
-            int codePoint = 0, i;
-            while (codePoint = DecodeUTF8Char(&text))
+            int codePoint = 0;
+            while ((codePoint = DecodeUTF8Char(&text)) != 0)
             {
                 if (codePoint > 0xFFFF)
                     FIXME("Support for UTF-16 surrgate pairs");