Skip empty maps when iterating over entries of LayeredImageHeapMap

Author: Zeavee

substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/util/LayeredImageHeapMap.java

@@ -193,10 +193,12 @@ public void remove() {
             public boolean advance() {
                 boolean advance = current.advance();
                 if (!advance) {
-                    if (cursors.hasNext()) {
+                    while (cursors.hasNext()) {
                         current = cursors.next();
-                        if (keys.add(current.getKey())) {
-                            return true;
+                        while (current.advance()) {
+                            if (keys.add(current.getKey())) {
+                                return true;
+                            }
                         }
                     }
                 }