TexStudio underlines in red an excerpt in which there are some double quotation marks, giving the error above.
I use
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
TexStudio underlines in red an excerpt in which there are some double quotation marks, giving the error above.
I use
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
U+FB01 is an fi ligature which should never be in your source file. So best would be to edit the input and replace it by fi but failing that
\DeclareUnicodeCharacter{FB01}{fi}
should work.