Fixes lookup of default configuration values for nested paths (#2322)

The lookup of default configuration values with multiple path segments failed with a class cast exception because the full path was treated as a new configuration section instead of only the root.

config/src/main/java/net/md_5/bungee/config/Configuration.java

@@ -56,7 +56,7 @@ public final class Configuration
         Object section = self.get( root );
         if ( section == null )
         {
-            section = new Configuration( ( defaults == null ) ? null : defaults.getSection( path ) );
+            section = new Configuration( ( defaults == null ) ? null : defaults.getSection( root ) );
             self.put( root, section );
         }
 

config/src/test/java/net/md_5/bungee/config/DefaultConfigurationTest.java

@@ -0,0 +1,22 @@
+package net.md_5.bungee.config;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public class DefaultConfigurationTest
+{
+    @Test
+    public void testDefaultValues()
+    {
+        Configuration defaultConfig = new Configuration();
+        defaultConfig.set( "setting", 10 );
+        defaultConfig.set( "nested.setting", 11 );
+        defaultConfig.set( "double.nested.setting", 12 );
+
+        Configuration actualConfig = new Configuration( defaultConfig );
+
+        Assert.assertEquals( 10, actualConfig.getInt( "setting" ) );
+        Assert.assertEquals( 11, actualConfig.getInt( "nested.setting" ) );
+        Assert.assertEquals( 12, actualConfig.getInt( "double.nested.setting" ) );
+    }
+}