Fix ends_at when cancelling paused subscriptions (#102)

Author: driesvints

src/Subscription.php

@@ -603,7 +603,9 @@ public function cancel()
         }
 
         if ($this->onPausedGracePeriod() || $this->paused()) {
-            $endsAt = $this->paused_from;
+            $endsAt = $this->paused_from->isFuture()
+                ? $this->paused_from
+                : Carbon::now();
         } else {
             $endsAt = $this->onTrial()
                 ? $this->trial_ends_at