BUG-2326 MAINT-2596 FIX crash when selecting non-existant user in resident picker

Added checks to validate that the selection list is non-empty

doc/contributions.txt

@@ -299,6 +299,7 @@ ChickyBabes Zuzu
 Christopher  Organiser
 Ciaran Laval
 Cinder Roxley
+    BUG-2326
     STORM-1703
 Clara Young
 Coaldust Numbers

indra/newview/llfloateravatarpicker.cpp

@@ -818,7 +818,14 @@ bool LLFloaterAvatarPicker::isSelectBtnEnabled()
 			uuid_vec_t avatar_ids;
 			std::vector<LLAvatarName> avatar_names;
 			getSelectedAvatarData(list, avatar_ids, avatar_names);
-			return mOkButtonValidateSignal(avatar_ids);
+			if (avatar_ids.size() >= 1) 
+			{
+				ret_val = mOkButtonValidateSignal(avatar_ids);
+			}
+			else
+			{
+				ret_val = false;
+			}
 		}
 	}