Removed assertions from Escrow and SplitPayment. (#1349)

(cherry picked from commit db2e1d2c746164f7460c6f311d9dc9d7b916e18a)

contracts/payment/Escrow.sol

@@ -40,7 +40,6 @@ contract Escrow is Secondary {
   */
   function withdraw(address payee) public onlyPrimary {
     uint256 payment = _deposits[payee];
-    assert(address(this).balance >= payment);
 
     _deposits[payee] = 0;
 

contracts/payment/SplitPayment.sol

@@ -85,7 +85,6 @@ contract SplitPayment {
     );
 
     require(payment != 0);
-    assert(address(this).balance >= payment);
 
     _released[account] = _released[account].add(payment);
     _totalReleased = _totalReleased.add(payment);