as soon as Pull Request #693 is merged (works flawless!) 
one should consider if alphanumeric "numbers" should also get an avatar.

this works for me:
```java
if ((recipient == null) || (recipient.getName() == null && (!Character.isLetter(recipient.getNumber().toCharArray()[0])))) {
//[...]
 char[] contactName = recipient.getName() != null ? recipient.getName().toCharArray() : recipient.getNumber().toCharArray();
```

same for the getColorForRecipient...