修复Sftp中exists方法父目录不存在时报错

hutool-extra/src/main/java/org/dromara/hutool/extra/ftp/AbstractFtp.java

@@ -136,6 +136,10 @@ public abstract class AbstractFtp implements Closeable {
 
 		// 文件验证
 		final String dir = StrUtil.defaultIfEmpty(StrUtil.removeSuffix(path, fileName), ".");
+		// issue#I7CSQ9 检查父目录为目录且是否存在
+		if(!isDir(dir)){
+			return false;
+		}
 		final List<String> names;
 		try {
 			names = ls(dir);