!1074 base64 NPE verification

Merge pull request !1074 from 蒋小小/v5-dev

hutool-core/src/main/java/cn/hutool/core/codec/Base64.java

@@ -30,6 +30,9 @@ public class Base64 {
 	 * @return 编码后的bytes
 	 */
 	public static byte[] encode(byte[] arr, boolean lineSep) {
+		if (arr == null) {
+			return null;
+		}
 		return lineSep ?
 				java.util.Base64.getMimeEncoder().encode(arr) :
 				java.util.Base64.getEncoder().encode(arr);
@@ -137,6 +140,9 @@ public class Base64 {
 	 * @return 被加密后的字符串
 	 */
 	public static String encode(byte[] source) {
+		if (source == null) {
+			return null;
+		}
 		return java.util.Base64.getEncoder().encodeToString(source);
 	}
 
@@ -148,6 +154,9 @@ public class Base64 {
 	 * @since 5.5.2
 	 */
 	public static String encodeWithoutPadding(byte[] source) {
+		if (source == null) {
+			return null;
+		}
 		return java.util.Base64.getEncoder().withoutPadding().encodeToString(source);
 	}
 
@@ -159,6 +168,9 @@ public class Base64 {
 	 * @since 3.0.6
 	 */
 	public static String encodeUrlSafe(byte[] source) {
+		if (source == null) {
+			return null;
+		}
 		return java.util.Base64.getUrlEncoder().withoutPadding().encodeToString(source);
 	}