Create a transaction for a write when the current content channel is not writable.

Fixes a NullPointerException, AR-1129.

git-svn-id: https://svn.alfresco.com/repos/alfresco-enterprise/alfresco/HEAD/root@4509 c4b6b30b-aa2e-2d43-bbcb-ca4b014f7261

source/java/org/alfresco/filesys/avm/AVMNetworkFile.java

@@ -467,6 +467,16 @@ public class AVMNetworkFile extends NetworkFile {
         }
     }
     
+    /**
+     * Return the writable state of the content channel
+     * 
+     * @return boolean
+     */
+    public final boolean isWritable()
+    {
+    	return m_writable;
+    }
+    
     /**
      * Return the network file details as a string
      *