Use the first non-empty line in the later error ouput
requested to merge work/359-insufficient-error-message-in-case-the-selected-font-cannot-be-found-by-the-used-latex-engine into master
When determining the error message in the latex output that is forwarded to the end-user, use the first non-empty line of the error output instead of the first line.
fix #359 (closed)