#1207 Customization: allow the implementation of interfaces by the mean of abstract classes

git-svn-id: http://svn.code.sf.net/p/itop/code/trunk@4193 a333f486-631f-4898-b8df-5754b55c2be0

core/metamodel.class.php

@@ -1619,7 +1619,7 @@ abstract class MetaModel
 			$oExtensionInstance = null;
 			foreach($aInterfaces as $sInterface)
 			{
-				if ($oRefClass->implementsInterface($sInterface))
+				if ($oRefClass->implementsInterface($sInterface) && $oRefClass->isInstantiable())
 				{
 					if (is_null($oExtensionInstance))
 					{