PluginClassLoader当apk直接调用PathClassLoader转换时报错bug

修改如下：
public class PluginClassLoader extends PathClassLoader {

public PluginClassLoader(String apkfile, String optimizedDirectory, String libraryPath, ClassLoader systemClassLoader) {
super(apkfile, libraryPath, systemClassLoader);

```
//获取pathList字段
try
{

//改写PathClassLoader的内容为DexClassLoader，这样客户端就可以使用PathClassLoader转换了
Class clazzPathLoader=Class.forName("dalvik.system.BaseDexClassLoader");
Class clazzPathList=Class.forName("dalvik.system.DexPathList");
Constructor ct = clazzPathList.getConstructor(ClassLoader.class,String.class,String.class,File.class);
Object oo=ct.newInstance(this,apkfile,libraryPath,new File(optimizedDirectory));
Field field=clazzPathLoader.getDeclaredField("pathList");
field.setAccessible(true);
field.set(this,oo);

}
catch(Exception ex)
{

}
}
```