🎨 优化部分代码，明确出错信息

Author: binarywang

weixin-java-common/src/main/java/me/chanjar/weixin/common/util/http/HttpResponseProxy.java

@@ -58,7 +58,7 @@ public String getFileName() throws WxErrorException {
   private String getFileName(CloseableHttpResponse response) throws WxErrorException {
     Header[] contentDispositionHeader = response.getHeaders("Content-disposition");
     if (contentDispositionHeader == null || contentDispositionHeader.length == 0) {
-      throw new WxErrorException("无法获取到文件名");
+      throw new WxErrorException("无法获取到文件名，Content-disposition为空");
     }
 
     return this.extractFileNameFromContentString(contentDispositionHeader[0].getValue());
@@ -76,15 +76,15 @@ private String getFileName(Response response) throws WxErrorException {
 
   private String extractFileNameFromContentString(String content) throws WxErrorException {
     if (content == null || content.length() == 0) {
-      throw new WxErrorException("无法获取到文件名");
+      throw new WxErrorException("无法获取到文件名，content为空");
     }
 
     Matcher m = PATTERN.matcher(content);
     if (m.matches()) {
       return m.group(1);
     }
 
-    throw new WxErrorException("无法获取到文件名");
+    throw new WxErrorException("无法获取到文件名，header信息有问题");
   }
 
 }