fix: crash when curUrl is nil.

Author: dujiepeng

Classes/ViewController/EaseCallMultiViewController.m

@@ -443,7 +443,7 @@ - (void)showNicknameAndAvartarForUsername:(NSString*)aUserName view:(UIView*)aVi
             streamView.nameLabel.text = [[EaseCallManager sharedManager] getNicknameByUserName:aUserName];
             NSURL* url = [[EaseCallManager sharedManager] getHeadImageByUserName:aUserName];
             NSURL* curUrl = [streamView.bgView sd_imageURL];
-            if(url && ![self isEquivalent:url with:curUrl]) {
+            if(!curUrl || (url && ![self isEquivalent:url with:curUrl])) {
                 [streamView.bgView sd_setImageWithURL:url completed:^(UIImage * _Nullable image, NSError * _Nullable error, SDImageCacheType cacheType, NSURL * _Nullable imageURL) {
 
                 }];