fix the premiumUploadSize validation to check the correct attribute

lib/load-config.js

@@ -38,7 +38,7 @@ if (!isPositiveNumber(config.defaultStorageLimit)) {
 
 // premiumUploadSize is worthless if it isn't a valid positive number
 // or if it's less than the default upload size
-if (!isPositiveNumber(config.premiumUploadSize) || config.premiumUploadSize < config.defaultStorageLimit) {
+if (!isPositiveNumber(config.premiumUploadSize) || config.premiumUploadSize < config.maxUploadSize) {
     delete config.premiumUploadSize;
 }