fix(server): Fix handling of ternary logic NULL in EventFilters #1487

Job	Run time
Debug Build & Unit Tests (gcc)	3m 5s
Debug Build & Unit Tests (gcc, 32bit)	3m 20s
Debug Build & Unit Tests without Subscriptions (gcc)	1m 42s
Debug Build & Unit Tests with Diagnostics (gcc)	2m 45s
Debug Build & Unit Tests with multithreading (gcc)	2m 1s
Debug Build & Unit Tests with Alarms&Conditions (gcc)	3m 17s
Debug Build & Unit Tests (clang)	4m 31s
Debug Build & Unit Tests (tcc)	2m 30s
Encryption (MbedTLS) Build & Unit Tests (gcc)	2m 26s
PubSub Encryption (MbedTLS) Build & Unit Tests (gcc)	2m 54s
PubSub SKS Build & Unit Tests (gcc)	3m 31s
Encryption (OpenSSL) Build & Unit Tests (gcc)	2m 23s
Encryption (LibreSSL) Build & Unit Tests (gcc)	5m 20s
TPM Tool Build	2m 28s
Release Build	1m 17s
Amalgamation Build	1m 0s
Amalgamation Build with Multithreading	54s
Valgrind Build & Unit Tests with MbedTLS (gcc)	27m 33s
Valgrind Build & Unit Tests with OpenSSL (gcc)	29m 14s
Valgrind Examples with MbedTLS (gcc)	58m 5s
Valgrind Examples with OpenSSL (gcc)	58m 15s
Clang Static Analyzer	3m 25s
Build All Companion Specifications	9m 16s
	3h 51m 12s

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