vulkan: fix fence initialization (#7038)

Previously, we have a VulkanSync with a default constructor that
allows us to have sync objects that returns error when
actual fences are not yet present.  We need to replicate that
with VulkanFence since sync objects have been removed from the
API.

Fixes #7034

filament/backend/src/vulkan/VulkanDriver.cpp

@@ -503,7 +503,7 @@ void VulkanDriver::destroyRenderTarget(Handle<HwRenderTarget> rth) {
 
 void VulkanDriver::createFenceR(Handle<HwFence> fh, int) {
     VulkanCommandBuffer const& commandBuffer = mCommands->get();
-    construct<VulkanFence>(fh, commandBuffer);
+    construct<VulkanFence>(fh, commandBuffer.fence);
 }
 
 void VulkanDriver::createSwapChainR(Handle<HwSwapChain> sch, void* nativeWindow, uint64_t flags) {
@@ -579,7 +579,7 @@ Handle<HwRenderTarget> VulkanDriver::createRenderTargetS() noexcept {
 }
 
 Handle<HwFence> VulkanDriver::createFenceS() noexcept {
-    return allocHandle<VulkanFence>();
+    return initHandle<VulkanFence>();
 }
 
 Handle<HwSwapChain> VulkanDriver::createSwapChainS() noexcept {
@@ -664,6 +664,12 @@ void VulkanDriver::destroyFence(Handle<HwFence> fh) {
 
 FenceStatus VulkanDriver::wait(Handle<HwFence> fh, uint64_t timeout) {
     auto& cmdfence = handle_cast<VulkanFence*>(fh)->fence;
+    if (!cmdfence) {
+        // If wait is called before a fence actually exists, we return timeout.  This matches the
+        // current behavior in OpenGLDriver, but we should eventually reconsider a different error
+        // code.
+        return FenceStatus::TIMEOUT_EXPIRED;
+    }
 
     // Internally we use the VK_INCOMPLETE status to mean "not yet submitted".
     // When this fence gets submitted, its status changes to VK_NOT_READY.

filament/backend/src/vulkan/VulkanHandles.h

@@ -129,7 +129,9 @@ struct VulkanRenderPrimitive : public HwRenderPrimitive {
 };
 
 struct VulkanFence : public HwFence {
-    explicit VulkanFence(const VulkanCommandBuffer& commands) : fence(commands.fence) {}
+    VulkanFence() = default;
+    explicit VulkanFence(std::shared_ptr<VulkanCmdFence> fence) : fence(fence) {}
+
     std::shared_ptr<VulkanCmdFence> fence;
 };