Submitted by hickuphh3, also found by eriksal1217 and shw
This is probably an oversight since SafeERC20 was imported and safeTransfer() was used for ERC20 token transfers. Nevertheless, note that approve() will fail for certain token implementations that do not return a boolean value (Eg. OMG and ADX tokens). Hence it is recommend to use safeApprove().
Recommend updating to _token.safeApprove(address(_native), totalToken) in tokenUnload().
Evert0x (Sherlock) confirmed
