Call forwarding fails due to setting null string as 'STRING=""', not 'STRING='. As a result test: IF($["${STRING}"=""]?TRUE:FALSE) generate syntax error.
Syntax error is generated in macro-dial-one, which gets variable set in macro-exten-vm (extensions_additional.conf):
[macro-exten-vm]
exten => s,n,Set(RT=${IF($["${ARG1}"!="novm" | "${DB(CFU/${EXTTOCALL})}"!="" | "${DB(CFB/${EXTTOCALL})}"!="" | ${ARG3} | ${ARG4} | ${ARG5}]?${RINGTIMER}:"")})
exten => s,n(macrodial),Macro(dial-one,${RT},${DIAL_OPTIONS},${EXTTOCALL})
[macro-dial-one]
exten => dlocal,1,Set(DSTRING=${IF($["${ARG1}"=""]?${DEXTEN:0:${MATH(${LEN(${DEXTEN})}-1,int)}}:Local/${DEXTEN:0:${MATH(${LEN(${DEXTEN})}-1,int)}}@from-internal/n)})
exten => dlocal,n,Set(USEGOTO=${IF($["${ARG1}"=""]?1:0)})
Personally, I changed line:
exten => s,n,Set(RT=${IF($["${ARG1}"!="novm" | "${DB(CFU/${EXTTOCALL})}"!="" | "${DB(CFB/${EXTTOCALL})}"!="" | ${ARG3} | ${ARG4} | ${ARG5}]?${RINGTIMER}:"")})
to
exten => s,n,Set(RT=${IF($["${ARG1}"!="novm" | "${DB(CFU/${EXTTOCALL})}"!="" | "${DB(CFB/${EXTTOCALL})}"!="" | ${ARG3} | ${ARG4} | ${ARG5}]?${RINGTIMER}:)})
(last characters differ) and it works, however I'm new to Asterisk.
Call Forward module version: 2.9.0.1
