clear sorting tag if collection is modified

platform/util/src/com/intellij/util/containers/SortedList.java

@@ -37,11 +37,13 @@ public class SortedList<T> extends AbstractList<T>{
 
   @Override
   public T remove(final int index) {
+    mySorted = false;
     return myDelegate.remove(index);
   }
 
   @Override
   public boolean remove(Object o) {
+    mySorted = false;
     ensureSorted();
     final int i = Collections.binarySearch(myDelegate, (T)o, myComparator);
     if (i >= 0) {