Log warning on invalid file size instead of printing a stack trace

src/net/java/sip/communicator/impl/protocol/jabber/extensions/thumbnail/FileElement.java

@@ -264,7 +264,8 @@ else if (elementName.equals("file"))
                         }
                         catch (NumberFormatException e)
                         {
-                            e.printStackTrace();
+                            logger.warn("Received an invalid file size,"
+                                + " continuing with fileSize set to 0", e);
                         }
                     }