ignore unmapped values

When a name is not mapped then the field should not be updated. This is
a bit weird and maybe should throw an error, but at least we avoid
chaning columns that are not meant to be changed.

query/query.go

@@ -80,6 +80,9 @@ func FieldMapToUpdate(fm types.FieldMap, nameMap map[string]string) (string, []i
 	i := 0
 	for key, val := range fm.Fields() {
 		if name, found := nameMap[key]; found {
+			if name == "" {
+				continue
+			}
 			i++
 			setClause = append(setClause, fmt.Sprintf("%s = $%d", name, i))
 			if val == "" {