coverity#1242531 Untrusted value as argument

Change-Id: I86e872251f7b8b0818a91c4a133f363e76be5f34

tools/source/generic/poly.cxx

@@ -1540,6 +1540,14 @@ SvStream& ReadPolygon( SvStream& rIStream, Polygon& rPoly )
 
     // read all points and create array
     rIStream.ReadUInt16( nPoints );
+
+    const size_t nMaxRecordsPossible = rIStream.remainingSize() / (2 * sizeof(sal_Int32));
+    if (nPoints > nMaxRecordsPossible)
+    {
+        SAL_WARN("tools", "Polygon claims " << nPoints << " records, but only " << nMaxRecordsPossible << " possible");
+        nPoints = nMaxRecordsPossible;
+    }
+
     if ( rPoly.mpImplPolygon->mnRefCount != 1 )
     {
         if ( rPoly.mpImplPolygon->mnRefCount )
@@ -1551,12 +1559,6 @@ SvStream& ReadPolygon( SvStream& rIStream, Polygon& rPoly )
 
     {
         // Determine whether we need to write through operators
-        const size_t nMaxRecordsPossible = rIStream.remainingSize() / (2 * sizeof(sal_Int32));
-        if (nPoints > nMaxRecordsPossible)
-        {
-            SAL_WARN("tools", "Polygon claims " << nPoints << " records, but only " << nMaxRecordsPossible << " possible");
-            nPoints = nMaxRecordsPossible;
-        }
 #if (SAL_TYPES_SIZEOFLONG) == 4
 #ifdef OSL_BIGENDIAN
         if ( rIStream.GetEndian() == SvStreamEndian::BIG )