Protect frame's owner property in frame.keep()
Protect frame's owner property in frame.keep()

Change-Id: I99d3bb2b09b72888d28ba35b0fc6f0a462337c46

IntelRealSense/librealsense,IntelRealSense/librealsense,IntelRealSense/librealsense,IntelRealSense/librealsense,IntelRealSense/librealsense,IntelRealSense/librealsense,IntelRealSense/librealsense,IntelRealSense/librealsense,IntelRealSense/librealsense