php-fpm doesn't accept empty values as environment variables.
It somewhat makes sense, as "" is actually the value
for an undefined environment variable.
Fixes the following issue:
[27-Feb-2020 12:00:23] ERROR: [/usr/local/etc/php-fpm-env.conf:9] empty value [27-Feb-2020 12:00:23] ERROR: Unable to include /usr/local/etc/php-fpm-env.conf from /usr/local/etc/php-fpm.conf at line 9 [27-Feb-2020 12:00:23] ERROR: failed to load configuration file '/usr/local/etc/php-fpm.conf' [27-Feb-2020 12:00:23] ERROR: FPM initialization failed
Ref T1598.