adding null sentinel value to gtable: PTFM-4247
adding null sentinel value to gtable: PTFM-4247

dnanexus/dx-toolkit,olegnev/dx-toolkit,dnanexus/dx-toolkit,johnwallace123/dx-toolkit,dnanexus/dx-toolkit,johnwallace123/dx-toolkit,jhuttner/dx-toolkit,johnwallace123/dx-toolkit,jhuttner/dx-toolkit,dnanexus/dx-toolkit,jhuttner/dx-toolkit,andyshinn/dx-toolkit,andyshinn/dx-toolkit,andyshinn/dx-toolkit,andyshinn/dx-toolkit,andyshinn/dx-toolkit,dnanexus/dx-toolkit,olegnev/dx-toolkit,andyshinn/dx-toolkit,andyshinn/dx-toolkit,olegnev/dx-toolkit,johnwallace123/dx-toolkit,jhuttner/dx-toolkit,olegnev/dx-toolkit,olegnev/dx-toolkit,dnanexus/dx-toolkit,dnanexus/dx-toolkit,johnwallace123/dx-toolkit,jhuttner/dx-toolkit,olegnev/dx-toolkit,jhuttner/dx-toolkit,johnwallace123/dx-toolkit,jhuttner/dx-toolkit,olegnev/dx-toolkit,dnanexus/dx-toolkit,andyshinn/dx-toolkit,jhuttner/dx-toolkit,olegnev/dx-toolkit,johnwallace123/dx-toolkit,johnwallace123/dx-toolkit