Don't use Qt::UniqueConnection on a lambda

It won't detect properly, instead the same code is moved into a member
function.

src/wayland/surface_interface.cpp

@@ -313,20 +313,7 @@ void SurfaceInterfacePrivate::surface_attach(Resource *resource, struct ::wl_res
         return;
     }
     pending.buffer = BufferInterface::get(compositor->display(), buffer);
-    QObject::connect(pending.buffer, &BufferInterface::aboutToBeDestroyed, q,
-        [this](BufferInterface *buffer) {
-            if (pending.buffer == buffer) {
-                pending.buffer = nullptr;
-            }
-            if (cached.buffer == buffer) {
-                cached.buffer = nullptr;
-            }
-            if (current.buffer == buffer) {
-                current.buffer->unref();
-                current.buffer = nullptr;
-            }
-        },
-        Qt::UniqueConnection);
+    QObject::connect(pending.buffer, &BufferInterface::aboutToBeDestroyed, q, &SurfaceInterface::handleBufferRemoved,  Qt::UniqueConnection);
 }
 
 void SurfaceInterfacePrivate::surface_damage(Resource *, int32_t x, int32_t y, int32_t width, int32_t height)
@@ -1011,4 +998,18 @@ QMatrix4x4 SurfaceInterface::surfaceToBufferMatrix() const
     return d->surfaceToBufferMatrix;
 }
 
+void SurfaceInterface::handleBufferRemoved(BufferInterface *buffer)
+{
+    if (d->pending.buffer == buffer) {
+        d->pending.buffer = nullptr;
+    }
+    if (d->cached.buffer == buffer) {
+        d->cached.buffer = nullptr;
+    }
+    if (d->current.buffer == buffer) {
+        d->current.buffer->unref();
+        d->current.buffer = nullptr;
+    }
+}
+
 } // namespace KWaylandServer

src/wayland/surface_interface.h

@@ -480,6 +480,8 @@ Q_SIGNALS:
     void committed();
 
 private:
+    void handleBufferRemoved(BufferInterface *buffer);
+
     QScopedPointer<SurfaceInterfacePrivate> d;
     friend class SurfaceInterfacePrivate;
 };