msxml3: Sign-compare warning fix

[Andrew Talbot]

Changelog:
    msxml3: Sign-compare warning fix.

diff --git a/dlls/msxml3/queryresult.c b/dlls/msxml3/queryresult.c
index d38cc19..e0367bc 100644
--- a/dlls/msxml3/queryresult.c
+++ b/dlls/msxml3/queryresult.c
@@ -308,7 +308,7 @@ static HRESULT queryresult_get_dispid(IUnknown *iface, BSTR name, DWORD flags, D
 {
     queryresult *This = impl_from_IXMLDOMNodeList( (IXMLDOMNodeList*)iface );
     WCHAR *ptr;
-    DWORD idx=0;
+    int idx = 0;
 
     for(ptr = name; *ptr && isdigitW(*ptr); ptr++)
         idx = idx*10 + (*ptr-'0');