diff --git a/main.go b/main.go
index 18473ce..ccc5051 100644
--- a/main.go
+++ b/main.go
@@ -1155,6 +1155,9 @@ func (s *appState) stopPreview() {
 }
 
 func toString(v interface{}) string {
+	if v == nil {
+		return ""
+	}
 	switch t := v.(type) {
 	case string:
 		return t