移除代码部分修改 code review by 高强

@@ -34,6 +34,11 @@ static float kprogressViewRadius = 2.0f;
     self.webView.delegate = nil;
     [self.webView removeFromSuperview];
     
+    self.progressBar = nil;
+    [self removeProgress];
+    self.progressView = nil;
+
+    
     self.webView = nil;
     
     if ([[NSURLCache sharedURLCache] isKindOfClass:[YHURLCache class]]) {
@@ -106,7 +111,9 @@ static float kprogressViewRadius = 2.0f;
  */
 - (void)removeProgress
 {
-    [self.progressView removeFromSuperview];
+    if (self.progressView) {
+        [self.progressView removeFromSuperview];
+    }
 }
 
 #pragma mark - Override Setter & Getter