Should had been sal_uInt64 nCount

Change-Id: I45b725ee740ea84f6af297338889dc447f279acd
Reviewed-on: https://gerrit.libreoffice.org/65104Reviewed-by: Eike Rathke <erack@redhat.com>
Tested-by: Jenkins

sc/inc/subtotal.hxx

@@ -47,7 +47,7 @@ public:
 private:
     double      fMean;
     double      fM2;
-    sal_Int64   nCount;
+    sal_uInt64  nCount;
 };
 
 struct ScFunctionData                   // to calculate single functions