HV-2113 Adding condition to validate a date

(cherry picked from commit cc29875)

Author: jundonghyuk

engine/src/main/java/org/hibernate/validator/internal/constraintvalidators/hv/kor/KorRRNValidator.java

@@ -87,7 +87,7 @@ private static boolean isValidChecksum(final String rrn) {
 		private static boolean isValidDate(final String rrn) {
 			final int month = extractMonth( rrn );
 			final int day = extractDay( rrn );
-			if ( month > 12 || day < 0 || day > 31 ) {
+			if ( month < 1 || month > 12 || day < 1 || day > 31 ) {
 				return false;
 			}
 			return day <= 31 && ( day <= 30 || ( month != 4 && month != 6 && month != 9 && month != 11 ) ) && ( day <= 29 || month != 2 );

engine/src/test/java/org/hibernate/validator/test/internal/constraintvalidators/hv/kor/KorRRNValidatorNeverAttrTest.java

@@ -70,6 +70,9 @@ void testNeverAttrWithoutHyphen() {
 	void invalidDate() {
 		assertInvalidRRN( "861324-2567481" );
 		assertInvalidRRN( "960292-2499371" );
+		assertInvalidRRN( "000001-1234560" );
+		assertInvalidRRN( "000100-1234560" );
+		assertInvalidRRN( "000000-1234560" );
 	}
 
 	// Invalid RRN Length