[cleanup] Fix error message in case of type error in AbstractExternalJavaAction

Change-Id: I0bb6fd0b40d12a3e38925e68dd1908167f88acf5
diff --git a/plugins/org.eclipse.sirius/src/org/eclipse/sirius/business/api/action/AbstractExternalJavaAction.java b/plugins/org.eclipse.sirius/src/org/eclipse/sirius/business/api/action/AbstractExternalJavaAction.java
index 9dc6993..a1a6f1e 100644
--- a/plugins/org.eclipse.sirius/src/org/eclipse/sirius/business/api/action/AbstractExternalJavaAction.java
+++ b/plugins/org.eclipse.sirius/src/org/eclipse/sirius/business/api/action/AbstractExternalJavaAction.java
@@ -81,7 +81,7 @@
             result = null;
         } else {
             String typeName = (value == null) ? "null" : ("a " + value.getClass().getSimpleName());
-            throw new IllegalArgumentException("Type error: parameter '" + name + "' should be a " + type.getClass().getSimpleName() + " but is " + typeName);
+            throw new IllegalArgumentException("Type error: parameter '" + name + "' should be a " + type.getSimpleName() + " but is " + typeName);
         }
         return result;
     }