When an account is edited, its color is lost

#### Steps to reproduce the behaviour
1. Set the color of an account
2. Edit the account.
3. Press save

#### Expected behaviour
The color of the account remains the same.

#### Actual behaviour
The color is unset.

#### Software specifications
* GnuCash Android version: 2.1.3
* System Android version: 5.0
* Device type: bq Aquaris E4
