pl/sql XMLTable INVALID_NUMBER error

I'm relatively new to pl/sql and xml.

I have an sql query that uses XMLTable to shred transaction details. When I run the query I get an INVALID_NUMBER error. If I comment out the 'Amount' element the query runs, so I'm assuming the problem lies here. I have no control over the content, so can't fix it. Is there any way to alter the XMLTable to either ignore the row with the error or do a decode to substitute zero when an invalid_number is found?

SELECT
      so.tranId
      , CHARGES.*
      FROM mytable1 so,
            XMLTABLE('//Charge' PASSING xmltype(so.xmlClob)
            COLUMNS "GeneralChargeID" NUMBER PATH 'GeneralChargeID',
                  "Name" VARCHAR2(255) PATH 'Name',
                  "Status" VARCHAR2(25) PATH 'Status',
                  "Quantity" NUMBER PATH 'Quantity',
                  "Amount" NUMBER(10,2) PATH 'Amount',
                  "CreditFlag" CHAR(1) PATH 'CreditFlag'                                
                  ) as CHARGES

I tried calling this statement, but the same error was thrown.
alter session set nls_numeric_characters=". ";