(proxy) fix template errors when nothing is configured

(cherry picked from commit 6c2e1467)

src/opnsense/service/templates/OPNsense/Proxy/newsyslog.conf

 # logfilename                   [owner:group]   mode    count size      when    flags   [/pid_file]               [sig_num]
-{% if OPNsense.proxy.general.enabled|default("0") == "1" %}
+{% if helpers.exists('OPNsense.proxy.general.enabled') and OPNsense.proxy.general.enabled|default("0") == "1" %}
 /var/log/squid/access.log   squid:squid     644     14       *      @T00     ZB      /var/run/squid/squid.pid       30
 /var/log/squid/cache.log    squid:squid     644     2       *       @T00     ZB      /var/run/squid/squid.pid       30
 /var/log/squid/store.log    squid:squid     644     2       *       @T00     ZB      /var/run/squid/squid.pid       30

src/opnsense/service/templates/OPNsense/Proxy/rc.conf.d

-squid_enable={% if OPNsense.proxy.general.enabled|default("0") == "1" %}YES{% else %}NO{% endif %}
+squid_enable={% if helpers.exists('OPNsense.proxy.general.enabled') and OPNsense.proxy.general.enabled|default("0") == "1" %}YES{% else %}NO{% endif %}
 
 squid_opnsense_bootup_run="/usr/local/opnsense/scripts/proxy/setup.sh"

src/opnsense/service/templates/OPNsense/Proxy/squid.conf

@@ -3,7 +3,7 @@
 # Do not edit this file manually.
 
 # setup listen configuration
-{%if OPNsense.proxy.forward.transparentMode == '1' %}
+{% if helpers.exists('OPNsense.proxy.forward.transparentMode') and OPNsense.proxy.forward.transparentMode == '1' %}
 # transparant mode, listen on localhost
 http_port 127.0.0.1:{{  OPNsense.proxy.forward.port }} intercept
 {% endif %}
@@ -276,7 +276,9 @@ cache_dir ufs {{OPNsense.proxy.general.cache.local.directory}} {{OPNsense.proxy.
 {%  endif %}
 {% endif %}
 
+{% if helpers.exists('OPNsense.proxy.general.cache.local') %}
 cache_mem {{ OPNsense.proxy.general.cache.local.cache_mem|default('256') }} MB
+{% endif %}
 
 # Leave coredumps in the first cache dir
 coredump_dir /var/squid/cache