[issue#3200]fix ClassCastException

easyexcel-core/src/main/java/com/alibaba/excel/util/ClassUtils.java

@@ -564,6 +564,7 @@ public class ClassUtils {
 
         FieldCacheKey(Class<?> clazz, ConfigurationHolder configurationHolder) {
             this.clazz = clazz;
+            if (configurationHolder instanceof WriteHolder) {
                 WriteHolder writeHolder = (WriteHolder)configurationHolder;
                 this.excludeColumnFieldNames = writeHolder.excludeColumnFieldNames();
                 this.excludeColumnIndexes = writeHolder.excludeColumnIndexes();
@@ -571,6 +572,7 @@ public class ClassUtils {
                 this.includeColumnIndexes = writeHolder.includeColumnIndexes();
             }
         }
+    }
 
     public static void removeThreadLocalCache() {
         FIELD_THREAD_LOCAL.remove();