Added ASSERT to detect when boundary condition appears multiple times.

library/SpatialDomains/Conditions.cpp

@@ -167,6 +167,10 @@ namespace Nektar
                 int err = regionElement->QueryIntAttribute("REF", &boundaryRegionID);
                 ASSERTL0(err == TIXML_SUCCESS, "Error reading boundary region reference.");
 
+                ASSERTL0(m_boundaryConditions.count(boundaryRegionID) == 0,
+                         "Boundary region '" + boost::lexical_cast<std::string>(boundaryRegionID)
+                         + "' appears multiple times.");
+
                 // Find the boundary region corresponding to this ID.
                 std::string boundaryRegionIDStr;
                 std::ostringstream boundaryRegionIDStrm(boundaryRegionIDStr);