tasks is immutable, must be not modified directly

platform/lang-impl/src/com/intellij/execution/impl/BaseExecuteBeforeRunDialog.java

@@ -1,18 +1,4 @@
-/*
- * Copyright 2000-2017 JetBrains s.r.o.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
+// Copyright 2000-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
 package com.intellij.execution.impl;
 
 import com.intellij.execution.*;
@@ -227,16 +213,19 @@ public abstract class BaseExecuteBeforeRunDialog<T extends BeforeRunTask> extend
     if (provider == null) {
       return;
     }
+
     T task = provider.createTask(config);
     update(task);
     task.setEnabled(true);
     if (enabled) {
       if (!tasks.contains(task)) {
+        tasks = new ArrayList<>(tasks);
         tasks.add(task);
       }
     }
     else {
       if (tasks.contains(task)) {
+        tasks = new ArrayList<>(tasks);
         tasks.remove(task);
       }
     }