bug 250838: do not fail if an unknown attribute type is found 

Signed-off-by: Florian Thienel <florian@thienel.org>
diff --git a/org.eclipse.vex.core/src/org/eclipse/vex/core/internal/validator/AttributeDefinition.java b/org.eclipse.vex.core/src/org/eclipse/vex/core/internal/validator/AttributeDefinition.java
index 7a15f6f..b175931 100644
--- a/org.eclipse.vex.core/src/org/eclipse/vex/core/internal/validator/AttributeDefinition.java
+++ b/org.eclipse.vex.core/src/org/eclipse/vex/core/internal/validator/AttributeDefinition.java
@@ -72,8 +72,8 @@
 			} else if (s.equals(ENUMERATION.toString()) || s.equals(CMDataType.ENUM)) {
 				return ENUMERATION;
 			} else {
-				throw new IllegalArgumentException("Attribute type '" + s
-						+ "' not recognized");
+				System.out.println("Found unknown attribute type '" + s + "'.");
+				return CDATA;
 			}
 		}