fix: 防止UIGraphicsBeginImageContextWithOptions闪退

Author: tbxark

NIMKit/NIMKit/Classes/Category/UIImage+NIMKit.m

@@ -290,6 +290,10 @@ - (UIImage *)nim_cropedImageWithSize:(CGSize)targetSize
     {
         return  self;
     }
+
+    if (targetSize.width <= 0 || targetSize.height <= 0) {
+        return self;
+    }
 
     if (targetSize.width / targetSize.height > sourceSize.width / sourceSize.height)
     {

NIMKit/NIMKit/Classes/Sections/Common/NIMAvatarImageView.m

@@ -101,6 +101,9 @@ - (void)setImage:(UIImage *)image
 
 - (UIImage*)imageAddCorner:(UIImage *)image radius:(CGFloat)radius andSize:(CGSize)size
 {
+    if (size.width <= 0 || size.height <= 0) {
+        return NULL;
+    }
     CGRect rect = CGRectMake(0, 0, size.width, size.height);
 
     UIGraphicsBeginImageContextWithOptions(size, NO, [UIScreen mainScreen].scale);