oleaut32: Handle negative offsets into the custom data table.

[Hans Leidekker]

Fixes a crash in the Visio 2002 installer.
---
 dlls/oleaut32/typelib.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/dlls/oleaut32/typelib.c b/dlls/oleaut32/typelib.c
index a5b0cdd..1cab886 100644
--- a/dlls/oleaut32/typelib.c
+++ b/dlls/oleaut32/typelib.c
@@ -1939,6 +1939,8 @@ static int MSFT_CustData( TLBContext *pcx, int offset, struct list *custdata_lis
 
     TRACE_(typelib)("\n");
 
+    if (pcx->pTblDir->pCDGuids.offset < 0) return 0;
+
     while(offset >=0){
         count++;
         pNew=heap_alloc_zero(sizeof(TLBCustData));
-- 
1.7.8.3