修复MultiResource游标歧义问题（issue#IDNAOY@Gitee）

hutool-core/src/main/java/cn/hutool/v7/core/io/resource/MultiResource.java

@@ -124,12 +124,12 @@ public class MultiResource implements Resource, Iterable<Resource>, Iterator<Res
 
 	@Override
 	public boolean hasNext() {
-		return cursor < resources.size();
+		return getValidCursor() < resources.size();
 	}
 
 	@Override
 	public synchronized Resource next() {
-		if (cursor >= resources.size()) {
+		if (!hasNext()) {
 			throw new ConcurrentModificationException();
 		}
 		this.cursor++;

hutool-core/src/test/java/cn/hutool/v7/core/io/resource/MultiResourceTest.java

@@ -284,10 +284,5 @@ class MultiResourceTest {
 			public InputStream getStream() {
 				return new ByteArrayInputStream(content.getBytes(StandardCharsets.UTF_8));
 			}
-
-			@Override
-			public boolean isModified() {
-				return false;
-			}
-		}
+	}
 }