libcamera: pipeline: virtual: Set FrameError on error

Do not cancel, simply set the buffer's status to `FrameError`
to notify the user about the error condition.

Signed-off-by: Barnabás Pőcze <pobrn@protonmail.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>

src/libcamera/pipeline/virtual/virtual.cpp

@@ -322,7 +322,7 @@ int PipelineHandlerVirtual::queueRequestDevice([[maybe_unused]] Camera *camera,
 
 				if (streamConfig.frameGenerator->generateFrame(
 					    stream->configuration().size, buffer))
-					buffer->_d()->cancel();
+					fmd.status = FrameMetadata::Status::FrameError;
 
 				completeBuffer(request, buffer);
 				break;