修复Convert.digitToChinese(0)输出金额无元整问题

hutool-core/src/main/java/cn/hutool/core/convert/Convert.java

@@ -1030,7 +1030,7 @@ public class Convert {
 	 */
 	public static String digitToChinese(Number n) {
 		if (null == n) {
-			return "零";
+			n = 0;
 		}
 		return NumberChineseFormatter.format(n.doubleValue(), true, true);
 	}

hutool-core/src/main/java/cn/hutool/core/convert/NumberChineseFormatter.java

@@ -92,7 +92,7 @@ public class NumberChineseFormatter {
 	 */
 	public static String format(double amount, boolean isUseTraditional, boolean isMoneyMode, String negativeName, String unitName) {
 		if (0 == amount) {
-			return "零";
+			return isMoneyMode ? "零元整" : "零";
 		}
 		Assert.checkBetween(amount, -99_9999_9999_9999.99, 99_9999_9999_9999.99,
 				"Number support only: (-99999999999999.99 ~ 99999999999999.99)！");

hutool-core/src/test/java/cn/hutool/core/convert/ConvertTest.java

@@ -435,4 +435,12 @@ public class ConvertTest {
 		Assert.assertEquals(12, s);
 	}
 
+	@Test
+	public void issue3662Test() {
+		String s = Convert.digitToChinese(0);
+		Assert.assertEquals("零元整", s);
+
+		s = Convert.digitToChinese(null);
+		Assert.assertEquals("零元整", s);
+	}
 }