Merge pull request #2386 from zhongwuzw/fix-nullable

Fix nullable key when cancel image load operation

SDWebImage/UIImageView+WebCache.h

@@ -27,8 +27,7 @@
     UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:MyIdentifier];
  
     if (cell == nil) {
-        cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:MyIdentifier]
-                 autorelease];
+        cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:MyIdentifier];
     }
  
     // Here we use the provided sd_setImageWithURL: method to load the web image

SDWebImage/UIView+WebCacheOperation.m

@@ -42,18 +42,21 @@ typedef NSMapTable<NSString *, id<SDWebImageOperation>> SDOperationsDictionary;
 }
 
 - (void)sd_cancelImageLoadOperationWithKey:(nullable NSString *)key {
-    // Cancel in progress downloader from queue
-    SDOperationsDictionary *operationDictionary = [self sd_operationDictionary];
-    id<SDWebImageOperation> operation;
-    @synchronized (self) {
-        operation = [operationDictionary objectForKey:key];
-    }
-    if (operation) {
-        if ([operation conformsToProtocol:@protocol(SDWebImageOperation)]){
-            [operation cancel];
-        }
+    if (key) {
+        // Cancel in progress downloader from queue
+        SDOperationsDictionary *operationDictionary = [self sd_operationDictionary];
+        id<SDWebImageOperation> operation;
+        
         @synchronized (self) {
-            [operationDictionary removeObjectForKey:key];
+            operation = [operationDictionary objectForKey:key];
+        }
+        if (operation) {
+            if ([operation conformsToProtocol:@protocol(SDWebImageOperation)]) {
+                [operation cancel];
+            }
+            @synchronized (self) {
+                [operationDictionary removeObjectForKey:key];
+            }
         }
     }
 }