Settle vendor open tractions

Hi Guys ... Hope you all r doing well....

I am facing a issue while going All vendors>> Settle open transactions (Invoice tab) >> then On this form when I am going on Withholding Tax Tab page then I m facing this error 

TaxWithhold_CustPaym object not initialized.

Stack trace

(C)\Forms\VendOpenTrans\Data Sources\TaxWithholdTrans\Methods\taxWithholdRoundOff - line 7

TaxWithhold_CustPaym object not initialized.

Stack trace

(C)\Forms\VendOpenTrans\Data Sources\TaxWithholdTrans\Methods\withholdOriginGross - line 7

TaxWithhold_CustPaym object not initialized.

Stack trace

(C)\Forms\VendOpenTrans\Data Sources\TaxWithholdTrans\Methods\taxWithholdExclude - line 7

Someone pls tell me how can i debug this issue

Thanks in advance