Merge pull request #931 from dart-lang/no-condition-in-for-2

For loops are not required to have a condition, take 2 (sdk issue 32588)
diff --git a/lib/src/util/condition_scope_visitor.dart b/lib/src/util/condition_scope_visitor.dart
index 411ba70..6fc1614 100644
--- a/lib/src/util/condition_scope_visitor.dart
+++ b/lib/src/util/condition_scope_visitor.dart
@@ -330,6 +330,7 @@
   /// not mean anything afterwards.
   bool _isRelevantOutsideOfForStatement(ForStatement node) =>
       !breakScope.hasBreak(node) &&
+      node.condition != null &&
       DartTypeUtilities
           .traverseNodesInDFS(node.condition)
           .where((n) => n is SimpleIdentifier)