Properly cancel code execution if running is prohibited

.rubocop_todo.yml

@@ -20,7 +20,7 @@ Metrics/CyclomaticComplexity:
   Max: 20
 
 Metrics/PerceivedComplexity:
-  Max: 23
+  Max: 25
 
 # We don't want to change previous migrations...
 #

app/controllers/submissions_controller.rb

@@ -110,7 +110,7 @@ class SubmissionsController < ApplicationController
       client_socket = tubesock
 
       client_socket.onopen do |_event|
-        return kill_client_socket(client_socket) if @embed_options[:disable_run]
+        kill_client_socket(client_socket) and return true if @embed_options[:disable_run]
       end
 
       client_socket.onclose do |_event|
@@ -160,6 +160,9 @@ class SubmissionsController < ApplicationController
       end
     end
 
+    # If running is not allowed (and the socket is closed), we can stop here.
+    return true if @embed_options[:disable_run]
+
     @testrun[:output] = +''
     durations = @submission.run(@file) do |socket, starting_time|
       runner_socket = socket