Fix stale size in AbstractMapMultiSet view iterator remove

src/main/java/org/apache/commons/collections4/multiset/AbstractMapMultiSet.java

@@ -92,7 +92,10 @@ public void remove() {
             if (!canRemove) {
                 throw new IllegalStateException("Iterator remove() can only be called once after next()");
             }
+            final int count = last.getCount();
             decorated.remove();
+            parent.size -= count;
+            parent.modCount++;
             last = null;
             canRemove = false;
         }
@@ -267,7 +270,8 @@ public void remove() {
             }
             final int count = parent.getCount(lastElement);
             super.remove();
-            parent.remove(lastElement, count);
+            parent.size -= count;
+            parent.modCount++;
             lastElement = null;
             canRemove = false;
         }

src/test/java/org/apache/commons/collections4/multiset/HashMultiSetTest.java

@@ -16,9 +16,12 @@
  */
 package org.apache.commons.collections4.multiset;
 
+import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
 
 import java.io.InvalidObjectException;
+import java.util.Iterator;
 
 import org.apache.commons.collections4.MultiSet;
 import org.junit.jupiter.api.Test;
@@ -44,6 +47,26 @@ public MultiSet<T> makeObject() {
         return new HashMultiSet<>();
     }
 
+    @Test
+    void testViewIteratorRemoveKeepsSizeConsistent() {
+        final HashMultiSet<String> multiset = new HashMultiSet<>();
+        multiset.add("a", 3);
+        final Iterator<String> unique = multiset.uniqueSet().iterator();
+        unique.next();
+        unique.remove();
+        assertEquals(0, multiset.size());
+        assertTrue(multiset.isEmpty());
+        assertEquals(0, multiset.toArray().length);
+
+        multiset.add("b", 4);
+        final Iterator<MultiSet.Entry<String>> entries = multiset.entrySet().iterator();
+        entries.next();
+        entries.remove();
+        assertEquals(0, multiset.size());
+        assertTrue(multiset.isEmpty());
+        assertEquals(0, multiset.toArray().length);
+    }
+
     @Test
     void testDeserializeRejectsNonPositiveCount() throws Exception {
         final int marker = 0x11223344;