mshtml: Avoid crash in nsIURI:Equals if other_url is NULL.

dlls/mshtml/nsio.c

diff --git a/dlls/mshtml/nsio.c b/dlls/mshtml/nsio.c
index 94004ab..b36f3fc 100644
--- a/dlls/mshtml/nsio.c
+++ b/dlls/mshtml/nsio.c
@@ -1754,7 +1754,7 @@
     }
 
     nsIWineURI_GetWineURL(wine_uri, &other_url);
-    *_retval = !UrlCompareW(This->wine_url, other_url, TRUE);
+    *_retval = other_url && !UrlCompareW(This->wine_url, other_url, TRUE);
     nsIWineURI_Release(wine_uri);
 
     return NS_OK;