Ensure modification count is checked properly

Author: dmulloy2

ProtocolLib/src/main/java/com/comphenix/protocol/injector/packet/MapContainer.java

@@ -1,5 +1,7 @@
 package com.comphenix.protocol.injector.packet;
 
+import static com.google.common.base.Preconditions.checkNotNull;
+
 import java.lang.reflect.Field;
 
 import com.comphenix.protocol.reflect.FieldUtils;
@@ -10,17 +12,20 @@
  */
 public class MapContainer {
 	// For detecting changes
-	private Field modCountField;
+	private final Field modCountField;
 	private int lastModCount;
 
 	// The object along with whether or not this is the initial run
-	private Object source;
+	private final Object source;
 	private boolean changed;
 
 	public MapContainer(Object source) {
 		this.source = source;
-		this.changed = true;
-		this.modCountField = FieldUtils.getField(source.getClass(), "modCount", true);
+		this.changed = false;
+
+		Field modCountField = FieldUtils.getField(source.getClass(), "modCount", true);
+		this.modCountField = checkNotNull(modCountField, "Failed to obtain modCount field");
+		this.lastModCount = getModificationCount();
 	}
 
 	/**
@@ -55,13 +60,13 @@ protected void checkChanged() {
 
 	/**
 	 * Retrieve the current modification count.
-	 * @return The current count, or something different than lastModCount if not accessible.
+	 * @return The current count
 	 */
 	private int getModificationCount() {
 		try {
-			return modCountField != null ? modCountField.getInt(source) : lastModCount + 1;
-		} catch (Exception e) {
-			throw new RuntimeException("Unable to retrieve modCount.", e);
+			return modCountField.getInt(source);
+		} catch (Exception ex) {
+			throw new RuntimeException("Unable to retrieve modCount.", ex);
 		}
 	}
 }