Check whether the enable attribute exists before fread
Check whether the enable attribute exists before fread

I think should check whether the enable attribute exists to determine
the return value, not raise an exception. Because it is not only that
the file does not exist that may cause IOError.

Signed-off-by: Zou Mingzhe <57b2a7cc15291240c8411253f0631bb00014668e@easystack.cn>

cvubrugier/rtslib-fb