Avoid NPE, profileFileSupplier can be null for tests (#5314)

Author: sugmanue

services/s3/src/main/java/software/amazon/awssdk/services/s3/internal/endpoints/UseGlobalEndpointResolver.java

@@ -82,6 +82,9 @@ private static String envVarSetting() {
 
     private String profileFileSetting(Supplier<ProfileFile> profileFileSupplier, Supplier<String> profileNameSupplier) {
         try {
+            if (profileFileSupplier == null || profileNameSupplier == null) {
+                return null;
+            }
             ProfileFile profileFile = profileFileSupplier.get();
             String profileName = profileNameSupplier.get();
             if (profileFile == null || profileName == null) {