Bump error-prone monorepo to v2.50.0

pom.xml

@@ -91,7 +91,7 @@
     <pitest-maven-plugin.version>1.25.4</pitest-maven-plugin.version>
     <pitest-junit5-plugin.version>1.2.3</pitest-junit5-plugin.version>
     <pitmute.version>1.1.0</pitmute.version>
-    <error-prone.version>2.49.0</error-prone.version>
+    <error-prone.version>2.50.0</error-prone.version>
     <nullaway.version>0.13.6</nullaway.version>
     <revapi-maven-plugin.version>0.15.1</revapi-maven-plugin.version>
     <revapi-java.version>0.28.4</revapi-java.version>

src/main/java/edu/hm/hafner/util/TreeStringBuilder.java

@@ -19,8 +19,15 @@
  * @author Kohsuke Kawaguchi
  */
 public class TreeStringBuilder {
+    /** Placeholder that represents no child node, until one is added. */
+    private static final Map<String, Child> NO_CHILDREN = Collections.emptyMap();
+
     private final Child root = new Child(new TreeString());
 
+    private Child getRoot() {
+        return root;
+    }
+
     /**
      * Interns a string.
      *
@@ -53,13 +60,6 @@ public void dedup() {
         getRoot().dedup(new HashMap<>());
     }
 
-    /** Placeholder that represents no child node, until one is added. */
-    private static final Map<String, Child> NO_CHILDREN = Collections.emptyMap();
-
-    Child getRoot() {
-        return root;
-    }
-
     /**
      * Child node that may store other elements.
      */