Remove incorrect iterator increment

Erase already goes to the next element.

Bug: 25738102
Change-Id: Iea31a7fb27ce9f810acf019a7b59dda7704b8f26
diff --git a/runtime/lambda/box_table.cc b/runtime/lambda/box_table.cc
index 8eef10b..9918bb7 100644
--- a/runtime/lambda/box_table.cc
+++ b/runtime/lambda/box_table.cc
@@ -62,7 +62,7 @@
 
 BoxTable::~BoxTable() {
   // Free all the copies of our closures.
-  for (auto map_iterator = map_.begin(); map_iterator != map_.end(); ++map_iterator) {
+  for (auto map_iterator = map_.begin(); map_iterator != map_.end(); ) {
     std::pair<UnorderedMapKeyType, ValueType>& key_value_pair = *map_iterator;
 
     Closure* closure = key_value_pair.first;