From 76468197d7618e0e354c3199a060f91255a0d8d4 Mon Sep 17 00:00:00 2001
From: Enno Rehling <enno.rehling@gmail.com>
Date: Sun, 12 Jul 2020 20:41:24 +0200
Subject: [PATCH] empty convoys cannot be built on.

---
 src/kernel/ship.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/src/kernel/ship.c b/src/kernel/ship.c
index 29867ca15..55cddbba8 100644
--- a/src/kernel/ship.c
+++ b/src/kernel/ship.c
@@ -146,12 +146,14 @@ void sunhash(ship * s)
 
 static ship *sfindhash(int i)
 {
-    ship *old;
+    ship *sh;
 
-    for (old = shiphash[i % MAXSHIPHASH]; old; old = old->nexthash)
-        if (old->no == i)
-            return old;
-    return 0;
+    for (sh  = shiphash[i % MAXSHIPHASH]; sh; sh = sh->nexthash) {
+        if (sh->no == i) {
+            return sh->number > 0 ? sh : NULL;
+        }
+    }
+    return NULL;
 }
 
 struct ship *findship(int i)