Bug 1621251 Replace NS_ADDREF(*var = other) with *var = do_AddRef(other).take() in /netwerk r=valentin

Differential Revision: https://phabricator.services.mozilla.com/D66818

netwerk/cache/nsDiskCacheDeviceSQL.cpp

@@ -682,11 +682,7 @@ nsApplicationCache::GetClientID(nsACString& out) {
 
 NS_IMETHODIMP
 nsApplicationCache::GetProfileDirectory(nsIFile** out) {
-  if (mDevice->BaseDirectory())
-    NS_ADDREF(*out = mDevice->BaseDirectory());
-  else
-    *out = nullptr;
-
+  *out = do_AddRef(mDevice->BaseDirectory()).take();
   return NS_OK;
 }