Throw exception when loading data from file failed

[arogachev]

Currently the empty array is returned:

https://github.com/yiisoft/rbac-php/blob/cb61807d57945f7ab6b930bc8a3b343f0787eb46/src/CommonStorage.php#L24-L34

[samdark]

That's checking if path is a file, not that it failed loading. On loading failure, an exception would be thrown. The reason for current code is for the file to be created automatically.