if forText is "" then _support's throwInvalidParameter(forText, "for", text, "Only contains characters ignored by the current considerations.") -- checks if all characters in forText are ignored by current considering/ignoring settings (the alternative would be to return each character as a non-match separated by a zero-length match, but that's probably not what the user intended); note that unlike `aString's length = 0`, which is what library code normally uses to check for empty text, on this occasion we do want to take into account the current considering/ignoring settings so deliberately use `forText is ""` here. For example, when ignoring punctuation, searching for the TID `"!?"` is no different to searching for `""`, because all of its characters are being ignored when comparing the text being searched against the text being searched for. Thus, a simple `forText is ""` test can be used to check in advance if the text contains any matchable characters under the current considering/ignoring settings, and report a meaningful error if not.