backends/wayland: Check whether it's possible to create a swapchain with the given format+modifier

BUG: 485496

src/backends/wayland/wayland_egl_backend.cpp

@@ -66,22 +66,18 @@ std::optional<OutputLayerBeginFrameInfo> WaylandEglPrimaryLayer::doBeginFrame()
     const QSize nativeSize = m_output->modeSize();
     if (!m_swapchain || m_swapchain->size() != nativeSize) {
         const QHash<uint32_t, QList<uint64_t>> formatTable = m_backend->backend()->display()->linuxDmabuf()->formats();
-        uint32_t format = DRM_FORMAT_INVALID;
-        QList<uint64_t> modifiers;
         for (const uint32_t &candidateFormat : {DRM_FORMAT_XRGB2101010, DRM_FORMAT_XRGB8888}) {
             auto it = formatTable.constFind(candidateFormat);
-            if (it != formatTable.constEnd()) {
-                format = it.key();
-                modifiers = it.value();
+            if (it == formatTable.constEnd()) {
+                continue;
+            }
+            m_swapchain = EglSwapchain::create(m_backend->drmDevice()->allocator(), m_backend->openglContext(), nativeSize, it.key(), it.value());
+            if (m_swapchain) {
                 break;
             }
         }
-        if (format == DRM_FORMAT_INVALID) {
-            qCWarning(KWIN_WAYLAND_BACKEND) << "Could not find a suitable render format";
-            return std::nullopt;
-        }
-        m_swapchain = EglSwapchain::create(m_backend->drmDevice()->allocator(), m_backend->openglContext(), nativeSize, format, modifiers);
         if (!m_swapchain) {
+            qCWarning(KWIN_WAYLAND_BACKEND) << "Could not find a suitable render format";
             return std::nullopt;
         }
     }