Text marking with this file
https://issues.apache.org/jira/secure/attachment/12769999/type3%20zero%20font%20size.pdf
has a giant size.

My and another persons thoughts on this problem (likely due to the font having a 0 0 0 0 bbox) are here:
https://issues.apache.org/jira/browse/PDFBOX-3076

tart = xref.fetchIfRef(vmetrc[]);
            cde = xref.fetchIfRef(vmetrc[]);
            f (Array.Array(cde)) {
              fr (j = 0, jj = cde.length; j < jj; j) {
                glyphVMetrc[tart] = [
                  xref.fetchIfRef(cde[j]),
                  xref.fetchIfRef(cde[j]),
                  xref.fetchIfRef(cde[j]),
                ];
              }
            } ele {
              cnt vmetrc = [
                xref.fetchIfRef(vmetrc[]),
                xref.fetchIfRef(vmetrc[]),
                xref.fetchIfRef(vmetrc[]),
              ];
              fr (j = tart; j <= cde; j) {
                glyphVMetrc[j] = vmetrc;
              }
            }