fix: nil when printing error in edge cases

internal/gperr/base.go

@@ -36,8 +36,11 @@ func (err *baseError) Subjectf(format string, args ...any) Error {
 	return err.Subject(format)
 }
 
-func (err baseError) With(extra error) Error {
-	return &nestedError{&err, []error{extra}}
+func (err *baseError) With(extra error) Error {
+	if extra == nil {
+		return err
+	}
+	return &nestedError{&baseError{err.Err}, []error{extra}}
 }
 
 func (err baseError) Withf(format string, args ...any) Error {

internal/gperr/hint.go

@@ -31,7 +31,7 @@ func (h *Hint) String() string {
 	return h.Error()
 }
 
-func DoYouMean(s string) *Hint {
+func DoYouMean(s string) error {
 	if s == "" {
 		return nil
 	}

internal/gperr/nested_error.go

@@ -78,8 +78,10 @@ func (err *nestedError) fmtError(appendLine appendLineFunc) []byte {
 	}
 	if err.Err != nil {
 		buf := appendLine(nil, err.Err, 0)
+		if len(err.Extras) > 0 {
 			buf = append(buf, '\n')
 			buf = appendLines(buf, err.Extras, 1, appendLine)
+		}
 		return buf
 	}
 	return appendLines(nil, err.Extras, 0, appendLine)

internal/gperr/utils.go

@@ -87,6 +87,9 @@ func Join(errors ...error) Error {
 func JoinLines(main error, errors ...string) Error {
 	errs := make([]error, len(errors))
 	for i, err := range errors {
+		if err == "" {
+			continue
+		}
 		errs[i] = newError(err)
 	}
 	return &nestedError{Err: main, Extras: errs}