UDA data type "numeric" declares 8 digit number as invalid

Hello,

I'm trying to use custom attributes (UDA's) to associate customer-ids and ticket-ids to my todos.
I've created a UDA called "ticket" with the following commands:

$ task config uda.ticket.type numeric
$ task config uda.ticket.label Ticket

When I was trying to add a todo with the following command, it fails with the message `The value '12345678' is not a valid numeric value.`:

$ task add Ask customer XY if he is happy customer:123456 ticket:12345678

While using 7 and 9 digit numbers works:


---
I don't think that it helps, but the template requested it, here is my `$ task diag` output (I've censored some names in file paths with *):
```
task 2.5.1
Platform: Darwin

Compiler
Version: 4.2.1 Compatible Apple LLVM 9.0.0 (clang-900.0.37)
Caps: +stdc +stdc_hosted +LP64 +c8 +i32 +l64 +vp64 +time_t64
Compliance: C++11

Build Features
Built: Sep 18 2017 12:51:06
CMake: 3.9.2
libuuid: libuuid + uuid_unparse_lower
libgnutls: 3.5.15
Build type: Release

Configuration
File: /Users/***/.taskrc (found), 1819 bytes, mode 100644
Data: /Users/***/.task (found), dir, mode 40755
Locking: Enabled
GC: Enabled
Server:
Trust: strict
Certificate: , not readable, 0 bytes
Key: , not readable, 0 bytes
Ciphers: NORMAL
Creds:

Hooks
System: Enabled
Location: /Users/***/.task/hooks
(-none-)

Tests
$TERM: xterm-256color (313x36)
Dups: Scanned 6 tasks for duplicate UUIDs:
No duplicates found
Broken ref: Scanned 6 tasks for broken references:
No broken references found
```