Allow permitted IPs to be null in the interactive installer

[mbernson]

When running vendor/bin/bunq-install the following error occurred:

PHP Fatal error:  Uncaught TypeError: Argument 1 passed to bunq\Util\InstallationUtil::formatIps() must be of the type string, null given, called in /Users/mbernson/bunqtest/vendor/bunq/sdk_php/src/Util/InstallationUtil.php on line 88 and defined in /Users/mbernson/bunqtest/vendor/bunq/sdk_php/src/Util/InstallationUtil.php:193
Stack trace:
#0 /Users/mbernson/bunqtest/vendor/bunq/sdk_php/src/Util/InstallationUtil.php(88): bunq\Util\InstallationUtil::formatIps(NULL)
#1 /Users/mbernson/bunqtest/vendor/bunq/sdk_php/bin/bunq-install(16): bunq\Util\InstallationUtil::interactiveInstall()
#2 {main}
  thrown in /Users/mbernson/bunqtest/vendor/bunq/sdk_php/src/Util/InstallationUtil.php on line 193

Fatal error: Uncaught TypeError: Argument 1 passed to bunq\Util\InstallationUtil::formatIps() must be of the type string, null given, called in /Users/mbernson/bunqtest/vendor/bunq/sdk_php/src/Util/InstallationUtil.php on line 88 and defined in /Users/mbernson/bunqtest/vendor/bunq/sdk_php/src/Util/InstallationUtil.php on line 193

TypeError: Argument 1 passed to bunq\Util\InstallationUtil::formatIps() must be of the type string, null given, called in /Users/mbernson/bunqtest/vendor/bunq/sdk_php/src/Util/InstallationUtil.php on line 88 in /Users/mbernson/bunqtest/vendor/bunq/sdk_php/src/Util/InstallationUtil.php on line 193

Call Stack:
    0.0003     354664   1. {main}() /Users/mbernson/bunqtest/vendor/bunq/sdk_php/bin/bunq-install:0
    0.0044     677128   2. bunq\Util\InstallationUtil::interactiveInstall() /Users/mbernson/bunqtest/vendor/bunq/sdk_php/bin/bunq-install:16
    9.4677    1736472   3. bunq\Util\InstallationUtil::formatIps() /Users/mbernson/bunqtest/vendor/bunq/sdk_php/src/Util/InstallationUtil.php:88

Error occurred on PHP 7.0.26, fix tested on PHP 7.0.26

[dnl-blkv]

Looks good!

[dnl-blkv]

@andrederoos