PDBfile parser fails with 'ArithmeticException' for some PDB entries

While executing the SIFTS N2NScan, I discovered that the PDBfile parser throws an Arithmetic exception caused by division by zero.

To reproduce, try fetching one of the following entries using the PDB sequence fetcher: 1a08; 1a09; 1a07; 1a1a; 1a1b; 1a1b; 1a1e.
    
Stack trace:

java.lang.ArithmeticException: / by zero
at MCview.PDBChain.makeCaBondList(PDBChain.java:255)
at MCview.PDBfile.makeCaBondList(PDBfile.java:518)
at MCview.PDBfile.parse(PDBfile.java:200)
at jalview.io.AlignFile.doParse(AlignFile.java:169)
at MCview.PDBfile.<init>(PDBfile.java:85)
at jalview.io.AppletFormatAdapter.readFile(AppletFormatAdapter.java:281)
at jalview.io.FormatAdapter.readFile(FormatAdapter.java:311)
at jalview.ws.dbsources.Pdb.getSequenceRecords(Pdb.java:134)
at jalview.gui.SequenceFetcher.run(SequenceFetcher.java:579)
at java.lang.Thread.run(Thread.java:745)
Failed to read alignment using the 'PDB' reader.
java.lang.ArithmeticException: / by zero
INFO : jalview.bin.Jalview - Error retrieving 1a08 from PDB
java.io.IOException: Formats currently supported are
BLC, CLUSTAL, FASTA, MSF, PileUp, PIR, PFAM, STH, PDB, JnetFile, RNAML, PHYLIP, JSON, GFF v2 or v3, and HTML.
at jalview.io.AppletFormatAdapter.readFile(AppletFormatAdapter.java:350)
at jalview.io.FormatAdapter.readFile(FormatAdapter.java:311)
at jalview.ws.dbsources.Pdb.getSequenceRecords(Pdb.java:134)
at jalview.gui.SequenceFetcher.run(SequenceFetcher.java:579)
at java.lang.Thread.run(Thread.java:745)
INFO - Error retrieving 1a08 from PDB
java.io.IOException: Formats currently supported are
BLC, CLUSTAL, FASTA, MSF, PileUp, PIR, PFAM, STH, PDB, JnetFile, RNAML, PHYLIP, JSON, GFF v2 or v3, and HTML.
at jalview.io.AppletFormatAdapter.readFile(AppletFormatAdapter.java:350)
at jalview.io.FormatAdapter.readFile(FormatAdapter.java:311)
at jalview.ws.dbsources.Pdb.getSequenceRecords(Pdb.java:134)
at jalview.gui.SequenceFetcher.run(SequenceFetcher.java:579)
at java.lang.Thread.run(Thread.java:745)