Fix nil event handler

Author: robacourt

packages/sync-service/lib/electric/shapes/consumer.ex

@@ -342,6 +342,11 @@ defmodule Electric.Shapes.Consumer do
     {:noreply, state, state.hibernate_after}
   end
 
+  def handle_info({:global_last_seen_lsn, _lsn}, %{event_handler: nil} = state) do
+    # Consumer not yet initialized, ignore
+    {:noreply, state}
+  end
+
   def handle_info({:global_last_seen_lsn, _lsn} = event, state) do
     case handle_event(event, state) do
       %{terminating?: true} = state ->