Fixed incorrect access to symbolic map records

Author: dog-m

approximations/src/main/java/runtime/LibSLRuntime.java

@@ -880,6 +880,8 @@ public static <K> boolean equals(final Map<K, ?> a, final Map<K, ?> b) {
         while (length != 0) {
             final K key = unseen.anyKey();
 
+            if (!b.hasKey(key))
+                return false;
             if (!equals(a.get(key), b.get(key)))
                 return false;