bug: If MountPoint.options is an empty string, an fstab is entry is corrupt

[bfjelds]

🔍 Description

When creating fstab entries, we try to ensure that "defaults" is used if a mount point has empty options:

        // If the options are empty, use "defaults" as the default
        let options = if self.options.is_empty() {
            "defaults".into()
        } else {
            self.options.join(",")
        };

We don't quite get this correct, as self.options is created from MountOptions.to_*_vec() into a Vec. Currently, at runtime self.options is a vector with one empty string element ([""]).

In this case, we create an fstab entry that is missing the options parameter, which means that the OS treats the subsequent parameter we create (0) as the options.

Proposed solution is to change MountOptions.to_*_vec() to filter empty strings.