Empty strings are not lowercase or uppercase

baked_in.go

@@ -2015,6 +2015,9 @@ func isLowercase(fl FieldLevel) bool {
 	field := fl.Field()
 
 	if field.Kind() == reflect.String {
+		if field.String() == "" {
+			return false
+		}
 		return field.String() == strings.ToLower(field.String())
 	}
 
@@ -2026,6 +2029,9 @@ func isUppercase(fl FieldLevel) bool {
 	field := fl.Field()
 
 	if field.Kind() == reflect.String {
+		if field.String() == "" {
+			return false
+		}
 		return field.String() == strings.ToUpper(field.String())
 	}
 

validator_test.go

@@ -9011,7 +9011,7 @@ func TestLowercaseValidation(t *testing.T) {
 	}{
 		{`abcdefg`, true},
 		{`Abcdefg`, false},
-		{"", true},
+		{"", false},
 	}
 
 	validate := New()
@@ -9048,7 +9048,7 @@ func TestUppercaseValidation(t *testing.T) {
 	}{
 		{`ABCDEFG`, true},
 		{`aBCDEFG`, false},
-		{"", true},
+		{"", false},
 	}
 
 	validate := New()