[whispersystems] Signal builds correctly with one error?

[Johan Wevers]

When I build Signal in Android Studio, the build succeeds but I get
always one error:

In ContactSelectionListAdapter.java on line 127:

int color = (contactType == ContactsDatabase.PUSH_TYPE) ?
drawables.getColor(0, 0xa0000000) : drawables.getColor(1, 0xff000000);

Error: Expected resource of type styleable [ResourceType]

It shows a read line under the "1" in the 2nd getColor() call. When I
expand it says something about annotations, but that is surpassing my
Java knowledge.

I don't see what's wrong there and the build succeeds (so it should be a
warning IMO, not an error). Any idea?