Particular combination of RNA secondary structure annotation braces causes endless loop in calculating helices

Certain particular configurations of braces in an RNA secondary structure annotation cause the helices calculation to go into an endless loop.
e.g. stockholm file (also attached)

# STOCKHOLM 1.0
#=GF ID RNA.SS.TEST
#=GF TP RNA;
Test.sequence AAAAAAAAAG
#=GC SS_cons ([[](()]))
//

My understanding of this might be limited, and such a brace combination might not be possible (and hence not catered for in the calculation).

The loop occurs when reading in the file, in
jalview.Analysis.Rna
in
getHelixMap(CharSequence rnaAnnotation)
lines 444-455:

      while (j >= 0)
      {
        int popen = bps.get(j).getBP5();

        // System.out.println("j " + j + " popen " + popen + " lastopen "
        // +lastopen + " open " + open);
        if ((popen < lastopen) && (popen > open))
        {
          if (helices.containsValue(popen)
                  && ((helices.get(popen)) == helix))
          {
            continue;
          }
...

which does not break out of the while loop as the j-=1 gets to a stage where it is not reached (j=2).