Fix possible infinite loop when Pi-hole ecosystem is not present

[DL6ER]

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The uninterruptible syscalls could have entered an infinite loop when logging that they can neither open nor create (due to missing permissions) the non-existing log file. Such a loop is now prevented.

[dschaper]

bash-5.1$ whoami
pihole
bash-5.1$ pihole-FTL -vv
****************************** FTL **********************************
Version:         vDev-6c5474e

****************************** dnsmasq ******************************
Version:         pi-hole-2.84
Compile options: IPv6 GNU-getopt no-DBus no-UBus no-i18n IDN DHCP DHCPv6 Lua TFTP no-conntrack ipset auth cryptohash DNSSEC loop-detect inotify dumpfile

****************************** SQLite3 ******************************
Version:         3.35.4
Compile options: COMPILER=gcc-9.3.0 DEFAULT_FOREIGN_KEYS OMIT_DEPRECATED OMIT_LOAD_EXTENSION OMIT_PROGRESS_CALLBACK THREADSAFE=1
******************************** LUA ********************************
Lua 5.4.1  Copyright (C) 1994-2020 Lua.org, PUC-Rio
bash-5.1$ pihole-FTL
Notice: Found no readable FTL config fileFATAL: Opening of FTL log (/var/log/pihole-FTL.log) failed!
       Make sure it exists and is writeable by user pihole

Completely nitpick but should there be a newline before the FATAL:?

[DL6ER]

@dschaper You are absolutely right, added.