demos: Fix compile warning setting renderPass
diff --git a/demos/cube.c b/demos/cube.c
index 0bccae0..e641a14 100644
--- a/demos/cube.c
+++ b/demos/cube.c
@@ -467,9 +467,9 @@
             .pNext = NULL,
             .flags = VK_CMD_BUFFER_OPTIMIZE_SMALL_BATCH_BIT |
                 VK_CMD_BUFFER_OPTIMIZE_ONE_TIME_SUBMIT_BIT,
-            .renderPass = VK_NULL_HANDLE,
+            .renderPass = { VK_NULL_HANDLE },
             .subpass = 0,
-            .framebuffer = VK_NULL_HANDLE,
+            .framebuffer = { VK_NULL_HANDLE },
         };
         err = vkBeginCommandBuffer(demo->cmd, &cmd_buf_info);
     }
@@ -509,9 +509,9 @@
         .sType = VK_STRUCTURE_TYPE_CMD_BUFFER_BEGIN_INFO,
         .pNext = NULL,
         .flags = VK_CMD_BUFFER_OPTIMIZE_SMALL_BATCH_BIT,
-        .renderPass = VK_NULL_HANDLE,
+        .renderPass = { VK_NULL_HANDLE },
         .subpass = 0,
-        .framebuffer = VK_NULL_HANDLE,
+        .framebuffer = { VK_NULL_HANDLE },
     };
     const VkClearValue clear_values[2] = {
         [0] = { .color.float32 = { 0.2f, 0.2f, 0.2f, 0.2f } },