For a file without translations, SvgFile::getInFileTranslations() currently returns text strings identified by the key fallback. However, SvgFile::getSavedLanguages() returns the languages of such a file with the key en (or whatever's given to SvgFile's constructor).
The latter should also be fallback.
Example with e.g. new SvgFile('InsertionIntoLinkedList1.svg', 'en'):
[ "trsvg1" => [ "fallback" => [...] ] ]
[ 0 => "en" ]