Update class-angelleye-paypal-ppcp-seller-onboarding.php

Added check for variable $paypal_vault_supported_country type to be an array.

Reason:
PHP Fatal error: Uncaught TypeError: in_array(): Argument angelleye#2 ($haystack) must be of type array, null given in wp-content/plugins/paypal-woocommerce/ppcp-gateway/class-angelleye-paypal-ppcp-seller-onboarding.php:142

ppcp-gateway/class-angelleye-paypal-ppcp-seller-onboarding.php

@@ -139,7 +139,7 @@ public function angelleye_generate_signup_link_with_feature($testmode, $page, $b
 
     public function angelleye_generate_signup_link_for_migration($testmode, $products) {
         $this->is_sandbox = ( $testmode === 'yes' ) ? true : false;
-        if (in_array($this->ppcp_paypal_country, $paypal_vault_supported_country) && angelleye_ppcp_is_subscription_support_enabled() === true) {
+        if (is_array($paypal_vault_supported_country) && in_array($this->ppcp_paypal_country, $paypal_vault_supported_country) && angelleye_ppcp_is_subscription_support_enabled() === true) {
             $body = $this->ppcp_vault_data();
         } else {
             $body = $this->default_data();