dd_lightbar_menu.js: Fix for substrWithAttrCodes(): If the given length is 0, then just return an empty string

Eric Oulashinrequested to merge
dd_lightbar_menu_substrWithAttrCodes_len_0 into master

dd_lightbar_menu.js: Fix for substrWithAttrCodes(): If the given length is 0, then just return an empty string

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