[folks] individual: Clarify that Individuals must contain at least one Persona

[Philip Withnall <pwithnall src gnome org>]

commit 7c57771050271705d06595f34ad08ab1ed71643f
Author: Philip Withnall <philip tecnocode co uk>
Date:   Fri Sep 21 15:19:46 2012 +0100

    individual: Clarify that Individuals must contain at least one Persona

 folks/individual.vala |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)
---
diff --git a/folks/individual.vala b/folks/individual.vala
index 04888bd..f301dd9 100644
--- a/folks/individual.vala
+++ b/folks/individual.vala
@@ -62,7 +62,8 @@ public enum Folks.TrustLevel
 
 /**
  * A physical person, aggregated from the various { link Persona}s the person
- * might have, such as their different IM addresses or vCard entries.
+ * might have, such as their different IM addresses or vCard entries. An
+ * individual must always contain at least one { link Persona}.
  *
  * When choosing the values of single-valued properties (such as
  * { link Individual.alias} and { link Individual.avatar}; but not multi-valued
@@ -941,6 +942,8 @@ public class Folks.Individual : Object,
   /**
    * The set of { link Persona}s encapsulated by this Individual.
    *
+   * There must always be at least one Persona in this set.
+   *
    * No order is specified over the set of personas, as such an order may be
    * different across each of the properties implemented by the personas (e.g.
    * should they be ordered by presence, name, star sign, etc.?).