chore: cleanup day 20

day20/main.go

@@ -65,9 +65,13 @@ func run(scan *bufio.Scanner) (*result, error) {
 
 	// rx is present.. perform part 2.
 	if rx, ok := receivers["rx"]; ok {
-		tip := m.m[rx[0]].(*conjunction) // panic if missing!
-
+		var tip *conjunction
 		var lvalues []int
+
+		if p, ok := m.m[rx[0]].(*conjunction); ok {
+			tip = p
+		}
+
 		for k, v := range tip.pushes {
 			for i, h := range makeHistory(v) {
 				if i == 1 && len(h) > 0 && h[0] > 0 {