vulkan: return VK_NOT_READY when no queries are available

Fixes a validation issue.
The issue is that the function gets called before we've sumitted a frame
for decoding to that context. However, we cannot run queries before
they've been reset, which happens at submission time.
As we'd need to otherwise run a command queue at init-time, just check
if submissions have happened.

libavutil/vulkan.c

@@ -456,6 +456,9 @@ VkResult ff_vk_exec_get_query(FFVulkanContext *s, FFVkExecContext *e,
     int64_t res = 0;
     VkQueryResultFlags qf = 0;
 
+    if (!e->had_submission)
+        return VK_NOT_READY;
+
     qf |= pool->query_64bit ?
           VK_QUERY_RESULT_64_BIT : 0x0;
     qf |= pool->query_statuses ?
@@ -779,6 +782,8 @@ int ff_vk_exec_submit(FFVulkanContext *s, FFVkExecContext *e)
         }
     }
 
+    e->had_submission = 1;
+
     return 0;
 }