Fix: Don't divide by zero

Signed-off-by: Knut Ahlers <knut@ahlers.me>

token.go

@@ -79,11 +79,16 @@ func (t tokenList) MinPeriod() int {
 	var m int = math.MaxInt32
 
 	for _, tok := range t {
-		if tok.Period < m {
+		if tok.Period != 0 && tok.Period < m {
 			m = tok.Period
 		}
 	}
 
+	if m == math.MaxInt32 {
+		// Fallback: Everything uses the default value
+		m = 30
+	}
+
 	return m
 }