GNAT Studio plugin is unable to display some graphs

[treiher]

This is caused by missing entries in the generated locations.json.

Example

% rflx graph -d generated specs/ipv4.rflx
Parsing specs/ipv4.rflx
Processing IPv4
Creating generated/IPv4_Option.svg
Creating generated/IPv4_Packet.svg

% cat generated/locations.json 
{"specs/ipv4.rflx": {"IPv4_Packet": {"start": {"line": 39, "column": 9}, "end": {"line": 62, "column": 18}}}}

The location for IPv4_Option is missing.