Web Wizard, ftp part: fix logic for dialog

Comment indicated "If one of these fields is empty, the button is disabled",
let's stick to this.

Cherry-picked from 2ff595db

Change-Id: I99dd23339d888c33e7706935842a91f5da681ade
Reviewed-on: https://gerrit.libreoffice.org/19112Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>
(cherry picked from commit 3a3fb3c5)

wizards/com/sun/star/wizards/web/FTPDialog.py

@@ -249,7 +249,7 @@ class FTPDialog(WizardDialog):
     # according to the status of the hostname, username, password text fields.
     # If one of these fields is empty, the button is disabled.
     def enableTestButton(self):
-        self.setEnabled(self.btnTestConnection, not self.isEmpty(self.host) or self.isEmpty(self.username) or self.isEmpty(self.password))
+        self.setEnabled(self.btnTestConnection, not (self.isEmpty(self.host) or self.isEmpty(self.username) or self.isEmpty(self.password)))
 
     # @param s
     # @return True if the string is None or "".