quartz: Simplify a loop and make the code more robust

[Bruno Jesus]

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diff --git a/dlls/quartz/avisplit.c b/dlls/quartz/avisplit.c
index 6059511..d0316cd 100644
--- a/dlls/quartz/avisplit.c
+++ b/dlls/quartz/avisplit.c
@@ -1109,15 +1109,14 @@ static HRESULT AVISplitter_InputPin_PreConnect(IPin * iface, IPin * pConnectPin,
         return E_FAIL;
     }
 
-    pos += sizeof(RIFFCHUNK) + list.cb;
-    hr = IAsyncReader_SyncRead(This->pReader, pos, sizeof(list), (BYTE *)&list);
-
-    while (list.fcc == ckidAVIPADDING || (list.fcc == FOURCC_LIST && list.fccListType != listtypeAVIMOVIE))
+    do
     {
+        list.fcc = 0;
         pos += sizeof(RIFFCHUNK) + list.cb;
-
         hr = IAsyncReader_SyncRead(This->pReader, pos, sizeof(list), (BYTE *)&list);
     }
+    while (hr == S_OK && (list.fcc == ckidAVIPADDING ||
+           (list.fcc == FOURCC_LIST && list.fccListType != listtypeAVIMOVIE)));
 
     if (list.fcc != FOURCC_LIST)
     {