Remove some assertions

[jj5]

You will find some code like this:

      assert( is_string( $result ) || $result === false );

      if ( is_string( $result ) || $result === false ) {

        return $result;

      }

      return $this->error( __FUNCTION__, KICKASS_CRYPTO_ERROR_RESULT_INVALID );

The problem is we can't test the error case because the assertion blows up. So remove all such assertions.