Fix #281 by moving the call that causes the NPE inside the check of 'isInLayout'

The method 'onCreateOptionsMenu' was inflating the menu when the check for 'isInLayout' returned false, but in 'onPrepareOptionsMenu' we were calling 'menu.findItem(R.id.menu_save_media).setVisible(false);' even when the menu was not inflated.
Check that currentBlog is not null. It should never happen here, that currentBlog == null, but an additional check doesn't hurt.