fix if cancelling print

git-svn-id: svn+ssh://svn.internal.sanger.ac.uk/repos/svn/pathsoft/artemis/trunk@8566 ee4ac58c-ac51-4696-9907-e4b3aa274f04

uk/ac/sanger/artemis/circular/PrintDNAImage.java

@@ -333,6 +333,8 @@ public class PrintDNAImage extends ScrollPanel
     format = new PageFormat();
 
     File file = showOptions();
+    if(file == null)
+      return;
     
     Dimension d = dna.getSize();
     double imageWidth  = d.getWidth();