Looks like it's probably a bug in [the parser](https://github.com/universal-ctags/ctags/blob/30cd8e034f34b218e9715ad8d406c3...), if you care to have a crack at fixing it.
Not a solution, but as a work-around you could probably use a line continuation (`_`) after the first string literal (before `mid()` call) to trick it into being parsed correctly.