only filter history if not empty

main.go

@@ -74,6 +74,7 @@ func main() {
 
 		l := len(history)
 
+		if l > 0 {
 			// wl-paste will always give back the last copied text
 			// (as long as the place we copied from is still running)
 			if history[l-1] == text {
@@ -89,6 +90,7 @@ func main() {
 
 			// remove duplicates
 			history = filter(history, text)
+		}
 
 		history = append(history, text)