dummy terms on function definition/scope

[swang203]

//for the following pyrope code

  $a as __bits:1
  $b as __bits:1
  %s as __bits:1
  %s = $a & $b

  fun1 = :($a,$b,%o):{
    %o = $a + $b
  }

// there will be two dummy null terms on the line of K9,
// I think this is the same issue as the closed issue #64
// this one should also be fixed

K1   K2    0  0    14   :    ___a    __bits  0d1                 
K2   K3    0  0    14   as   $a      ___a                        
K3   K4    0  15   29   :    ___b    __bits  0d1                 
K4   K5    0  15   29   as   $b      ___b                        
K5   K6    0  30   44   :    ___c    __bits  0d1                 
K6   K7    0  30   44   as   %s      ___c                        
K7   K8    0  45   57   &    ___d    $a      $b                  
K8   K9    0  45   57   =    %s      ___d                        
K11  K12   1  59   96   +    ___f    $a      $b                  
K12  null  1  59   96   =    %o      ___f                        
K9   K14   0  59   96   ::{  ___e    null    K11   $a    $b  %o  null