Bug #44568 -> don't fall out and not open the url if we failed to set the load

attributes on a channel. This broke mailto urls because the mailto channel
is just a stub and doesn't implement this method.
r=valeski

docshell/base/nsDocShell.cpp

@@ -2973,7 +2973,7 @@ NS_IMETHODIMP nsDocShell::DoChannelLoad(nsIChannel *aChannel, nsURILoadCommand a
 			break;
    }
    
-   NS_ENSURE_SUCCESS(aChannel->SetLoadAttributes(loadAttribs), NS_ERROR_FAILURE);
+   (void) aChannel->SetLoadAttributes(loadAttribs);
 
    NS_ENSURE_SUCCESS(aURILoader->OpenURI(aChannel, aLoadCmd,
       aWindowTarget, NS_STATIC_CAST(nsIDocShell*, this)), NS_ERROR_FAILURE);