in remainingSize consider that its is possible to seek past the end

Change-Id: I1652244d5515629f1cd8f15f4c5b15f139dba0aa

tools/source/stream/stream.cxx

@@ -1453,7 +1453,7 @@ sal_uInt64 SvStream::remainingSize()
 {
     sal_uInt64 const nCurr = Tell();
     sal_uInt64 const nEnd = Seek(STREAM_SEEK_TO_END);
-    sal_uInt64 nMaxAvailable = nEnd-nCurr;
+    sal_uInt64 nMaxAvailable = nEnd > nCurr ? (nEnd-nCurr) : 0;
     Seek(nCurr);
     return nMaxAvailable;
 }