Fix various issues reported by Coverity

degesch.c

@@ -5003,7 +5003,10 @@ irc_handle_nick (struct server *s, const struct irc_message *msg)
 
 		user_unref (buffer_collision->user);
 		buffer_collision->user = user_ref (user);
+	}
 
+	if (pm_buffer && buffer_collision)
+	{
 		// There's not much else we can do other than somehow try to merge
 		// one buffer into the other.  In our case, the original buffer wins.
 		buffer_merge (s->ctx, buffer_collision, pm_buffer);
@@ -6265,7 +6268,7 @@ static void
 config_dump_children
 	(struct config_item_ *object, struct config_dump_data *data)
 {
-	hard_assert (object->type = CONFIG_ITEM_OBJECT);
+	hard_assert (object->type == CONFIG_ITEM_OBJECT);
 
 	struct config_dump_level level;
 	level.next = NULL;
@@ -7788,6 +7791,7 @@ process_user_command
 	struct command_handler *handler;
 	if (!(handler = str_map_find (&map, command_name)))
 		return false;
+	hard_assert (handler->flags == 0 || (handler->flags & HANDLER_SERVER));
 
 	if ((handler->flags & HANDLER_SERVER)
 		&& args.buffer->type == BUFFER_GLOBAL)
@@ -8036,7 +8040,7 @@ static size_t
 utf8_common_prefix (const char **vector, size_t len)
 {
 	size_t prefix = 0;
-	if (!vector || !vector[0])
+	if (!vector || !len)
 		return 0;
 
 	struct utf8_iter a[len];

kike.c

@@ -1818,8 +1818,11 @@ mode_processor_do_list (struct mode_processor *self,
 		return;
 	}
 
+	if (!mode_processor_check_operator (self))
+		return;
+
 	char *mask = irc_check_expand_user_mask (target);
-	if (!mode_processor_check_operator (self) || !mask)
+	if (!mask)
 		return;
 
 	size_t i;

zyklonb.c

@@ -673,13 +673,12 @@ prepare_recovery_environment (void)
 			break;
 	}
 
-	if (iter)
+	if (*iter)
 		g_startup_reason_location = iter;
 	else
 	{
+		g_startup_reason_location = g_recovery_env.vector + g_recovery_env.len;
 		str_vector_add (&g_recovery_env, "");
-		g_startup_reason_location =
-			g_recovery_env.vector + g_recovery_env.len - 1;
 	}
 }