Command does not expand when there are non ascii characters before

* What command(s) did you run?
```task add köp mjölk proj```
* What did you expect to happen?
The command completes to
```task add köp mjölk project:```

* What actually happened?
Nothing

* Paste the output of the ```task diag``` command.

task 2.5.1
Platform: Linux

Compiler
Version: 7.2.0
Caps: +stdc +stdc_hosted +LP64 +c8 +i32 +l64 +vp64 +time_t64
Compliance: C++11

Build Features
CMake: 3.9.5
libuuid: libuuid + uuid_unparse_lower
libgnutls: 3.5.8
Build type: None

Configuration
File: /home/voidcase/.taskrc (found), 1461 bytes, mode 100644
Data: /home/voidcase/Sync/.task (found), dir, mode 40755
Locking: Enabled
GC: Enabled
$EDITOR: /usr/bin/nvim
Server:
Trust: strict
Certificate: , not readable, 0 bytes
Key: , not readable, 0 bytes
Ciphers: NORMAL
Creds:

Hooks
System: Enabled
Location: /home/voidcase/Sync/.task/hooks
(-none-)

Tests
$TERM: xterm-256color (120x30)
Dups: Scanned 43 tasks for duplicate UUIDs:
No duplicates found
Broken ref: Scanned 43 tasks for broken references:
No broken references found