Throw a more detailed error when database connection info is missing

common/src/main/java/me/lucko/luckperms/common/dependencies/classloader/IsolatedClassLoader.java

@@ -44,7 +44,7 @@ public class IsolatedClassLoader extends URLClassLoader {
          * ClassLoader#getSystemClassLoader returns the AppClassLoader
          *
          * Calling #getParent on this returns the ExtClassLoader (Java 8) or
-         * the PlatformClassLoader (Java 8). Since we want this classloader to
+         * the PlatformClassLoader (Java 9). Since we want this classloader to
          * be isolated from the Minecraft server (the app), we set the parent
          * to be the platform class loader.
          */

common/src/main/java/me/lucko/luckperms/common/storage/StorageCredentials.java

@@ -26,6 +26,7 @@
 package me.lucko.luckperms.common.storage;
 
 import java.util.Map;
+import java.util.Objects;
 
 public class StorageCredentials {
 
@@ -52,19 +53,19 @@ public class StorageCredentials {
     }
 
     public String getAddress() {
-        return this.address;
+        return Objects.requireNonNull(this.address, "address");
     }
 
     public String getDatabase() {
-        return this.database;
+        return Objects.requireNonNull(this.database, "database");
     }
 
     public String getUsername() {
-        return this.username;
+        return Objects.requireNonNull(this.username, "username");
     }
 
     public String getPassword() {
-        return this.password;
+        return Objects.requireNonNull(this.password, "password");
     }
 
     public int getMaxPoolSize() {

common/src/main/java/me/lucko/luckperms/common/treeview/PermissionRegistry.java

@@ -111,7 +111,7 @@ public class PermissionRegistry extends RepeatingTask {
         // insert the permission into the node structure
         TreeNode current = this.rootNode;
         for (String part : parts) {
-            current = current.getChildMap().computeIfAbsent(part, s -> new TreeNode());
+            current = current.resolve(part);
         }
     }
 

common/src/main/java/me/lucko/luckperms/common/treeview/TreeNode.java

@@ -38,13 +38,17 @@ public class TreeNode {
     private Map<String, TreeNode> children = null;
 
     // lazy init
-    public synchronized Map<String, TreeNode> getChildMap() {
+    private synchronized Map<String, TreeNode> getChildMap() {
         if (this.children == null) {
             this.children = new ConcurrentHashMap<>();
         }
         return this.children;
     }
 
+    public TreeNode resolve(String s) {
+        return getChildMap().computeIfAbsent(s, x -> new TreeNode());
+    }
+
     public Optional<Map<String, TreeNode>> getChildren() {
         return Optional.ofNullable(this.children);
     }