Hydra/Event: fix scalar context warning

Dependencies

• [2] EKHD4I44 Event: init structure and parse existing messages
• [3] GQGQEMMA Event.pm: add a new_event helper to parse and construct an Event

Change contents

• replacement in src/lib/Hydra/Event.pm at line 20
  [2.2759]→[2.2759:2812](∅→∅)
  − my $parser = %channels_to_events{$channel_name};
  [2.2759]

  [2.2812]
  + my $parser = $channels_to_events{$channel_name};