fix: ignore nil query (#6021)

statement.go

@@ -311,6 +311,9 @@ func (stmt *Statement) BuildCondition(query interface{}, args ...interface{}) []
 	conds := make([]clause.Expression, 0, 4)
 	args = append([]interface{}{query}, args...)
 	for idx, arg := range args {
+		if arg == nil {
+			continue
+		}
 		if valuer, ok := arg.(driver.Valuer); ok {
 			arg, _ = valuer.Value()
 		}

statement_test.go

@@ -35,6 +35,13 @@ func TestWhereCloneCorruption(t *testing.T) {
 	}
 }
 
+func TestNilCondition(t *testing.T) {
+	s := new(Statement)
+	if len(s.BuildCondition(nil)) != 0 {
+		t.Errorf("Nil condition should be empty")
+	}
+}
+
 func TestNameMatcher(t *testing.T) {
 	for k, v := range map[string][]string{
 		"table.name":         {"table", "name"},