KFilePropsPlugin: don't disable the OK dialog button if the file name is readonly
Calling KPropertiesDialog::setFileNameReadOnly() hides and empties the fileNameLineEdit, but this also has the side effect of disabling the OK button on the whole dialog. Since setFileNameReadOnly() is a one-way method (once it's read-only it can't be switched back to read-write), just disconnect the signal just before fileNameLineEdit gets emptied, avoiding the call to KFilePropsPlugin::nameFileChanged() that disables the OK button. Can be tested opening the properties dialog of an "icon" application applet