SDL: main: Check for SDL_AddEventWatch failure, now that it can report it.

SDL Commits
1 
From 019468dc59ebb810ad705fc96577e210fe0c7657 Mon Sep 17 00:00:00 2001
From: "Ryan C. Gordon" <[EMAIL REDACTED]>
Date: Sat, 4 Nov 2023 09:31:07 -0400
Subject: [PATCH] main: Check for SDL_AddEventWatch failure, now that it can
 report it.

---
 src/main/SDL_main_callbacks.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/main/SDL_main_callbacks.c b/src/main/SDL_main_callbacks.c
index 2ac9abaf8f5a..076c842597ba 100644
--- a/src/main/SDL_main_callbacks.c
+++ b/src/main/SDL_main_callbacks.c
@@ -67,7 +67,11 @@ int SDL_InitMainCallbacks(int argc, char* argv[], SDL_AppInit_func appinit, SDL_
             total_pending_events++;
         }
 
-        SDL_AddEventWatch(EventWatcher, NULL);  // !!! FIXME: this should really return an error.
+        if (SDL_AddEventWatch(EventWatcher, NULL) == -1) {
+            SDL_free(pending_events);
+            SDL_AtomicSet(&apprc, -1);
+            return -1;
+        }
 
         for (int i = 0; i < total_pending_events; i++) {
             SDL_PushEvent(&pending_events[i]);