backends/drm: Mark frame failed if presenting null buffer

If eglSwapBuffers() fails, there won't be a buffer and so we need to
mark the frame as failed. Otherwise, the screen can be frozen.

eglSwapBuffers() can fail if some effect calls makeOpenGLContext()
between RenderBackend::beginFrame() and RenderBackend::endFrame(), which
is the case with the zoom effect. It can set wrong draw surface in
ZoomEffect::recreateTexture()

BUG: 445412

src/backends/drm/drm_output.cpp

@@ -372,6 +372,7 @@ bool DrmOutput::needsSoftwareTransformation() const
 bool DrmOutput::present(const QSharedPointer<DrmBuffer> &buffer, QRegion damagedRegion)
 {
     if (!buffer || buffer->bufferId() == 0) {
+        presentFailed();
         return false;
     }
     RenderLoopPrivate *renderLoopPrivate = RenderLoopPrivate::get(m_renderLoop);

src/backends/drm/drm_pipeline.cpp

@@ -47,12 +47,7 @@ DrmPipeline::~DrmPipeline()
 bool DrmPipeline::present(const QSharedPointer<DrmBuffer> &buffer)
 {
     Q_ASSERT(pending.crtc);
-    if (!buffer) {
-        if (m_output) {
-            m_output->presentFailed();
-        }
-        return false;
-    }
+    Q_ASSERT(buffer);
     m_primaryBuffer = buffer;
     auto buf = dynamic_cast<DrmGbmBuffer*>(buffer.data());
     // with direct scanout disallow modesets, calling presentFailed() and logging warnings