973848 - ISE in case no file specified when crating key   &&  Check if the key is not empty file when editing

There are two problems address by this PR.
1. We need to check  if the key is not empty file  not only when creating the key but also when editing/updating it.
2. Commit 81b5811 introduces ISE - Unhandled Exception thrown: class java.lang.NullPointerException in:
code/src/com/redhat/rhn/frontend/struts/StrutsDelegate.java
public void addError(ActionErrors errors, String msgKey, Object...params) {
ActionMessages msg = new ActionMessages();
msg.add(ActionMessages.GLOBAL_MESSAGE, new ActionMessage(msgKey,
params));
errors.add(msg);
}