fix: size ordering of ambigous mappings not correct, fix ##380.

Author: jrfaller

core/src/main/java/com/github/gumtreediff/matchers/heuristic/gt/GreedySubtreeMatcher.java

@@ -56,7 +56,7 @@ public static class AmbiguousMappingsComparator implements Comparator<Pair<Set<T
         @Override
         public int compare(Pair<Set<Tree>, Set<Tree>> m1, Pair<Set<Tree>, Set<Tree>> m2) {
             int s1 = m1.first.stream().max(Comparator.comparingInt(t -> t.getMetrics().size)).get().getMetrics().size;
-            int s2 = m1.first.stream().max(Comparator.comparingInt(t -> t.getMetrics().size)).get().getMetrics().size;
+            int s2 = m2.first.stream().max(Comparator.comparingInt(t -> t.getMetrics().size)).get().getMetrics().size;
             return Integer.compare(s2, s1);
         }
     }