Fixed bug 1923 - Crash with SDL_SetColorKey

Sylvain

1/ Load an Image XPM with IMG_ReadXPMFromArray()
2/ Try to set a ColorKey on it.

I notice that :
- the SDL_Surface that is created from XPM has a palette !
- the colorkey is a RBG.

it crashes (SIGSEGV) inside the SDL_SetColorKey function:
"surface->format->palette->colors[surface->map->info.colorkey].a"

src/video/SDL_surface.c

@@ -175,7 +175,11 @@ SDL_SetColorKey(SDL_Surface * surface, int flag, Uint32 key)
     int flags;
 
     if (!surface) {
-        return -1;
+        return SDL_InvalidParamError("surface");
+    }
+
+    if (surface->format->palette && key >= surface->format->palette->ncolors) {
+        return SDL_InvalidParamError("key");
     }
 
     if (flag & SDL_RLEACCEL) {