Fixed warning: initialization of pointer of type 'VkSampler' (aka 'struct VkSampler_T *') to null from a constant boolean expression

Fixes https://github.com/libsdl-org/SDL/issues/13628

src/render/vulkan/SDL_render_vulkan.c

@@ -3760,7 +3760,7 @@ static VkSampler VULKAN_GetSampler(VULKAN_RenderData *data, SDL_ScaleMode scale_
         VkResult result = vkCreateSampler(data->device, &samplerCreateInfo, NULL, &data->samplers[key]);
         if (result != VK_SUCCESS) {
             SET_ERROR_CODE("vkCreateSampler()", result);
-            return false;
+            return VK_NULL_HANDLE;
         }
     }
     return data->samplers[key];