[Search files] fix preview for files with spaces (again)

[PatrickF1]

Apparently, I didn't actually fix this bug when I tried to fix it in #137

[PatrickF1]

@kidonng Ok this fixes bug 1 from #137 but it introduces a new bug, which I shall call bug 3. To repro

1. mkdir -p "normal/with spaces"
2. touch "normal/with spaces"/{1,2,3}
3. execute search directory with cursor on normal/
4. Notice you can't preview the files in normal

I realized both of these bugs actually weren't a problem until #137, so I must have broke something trying to fix something else. So confused...this is what I was afraid of when introducing all of these features to search directory. Never mind going back to the commit before #137, I was able to repro bug 1 but not bug 3.

[kidonng]

(Sigh) We could have settled on this from the beginning. Thanks for the fix!

[PatrickF1]

Yeah, that was my bad. I should have investigated closer. I've been pretty demotivated about maintaining this feature. It's been quite a thorn in my side siphoning my time for other feature I'd rather work on.

[kidonng]

I don't want to see you feeling bad about all these issues, but I have to say this issue (Bug 2 in #137 (comment)) is still no fixed.

To reproduce, set $fzf_preview_dir_cmd and search with a base directory with spaces in its name: