gdd: fix issue when copying from an emtpy array

if the source array is empty, the index of the first element to copy (0) being equal
   to the source array size (0) does not constitute an out-of-bounds condition

src/gdd/gdd.cc

@@ -1353,7 +1353,7 @@ gddStatus gdd::put ( const gdd * dd )
         // clip to upper limit of source
         aitUint32 srcCopySize;
         const aitUint32 unusedSrcBelow = srcCopyFirst - srcFirst;
-        if ( srcElemCount <= unusedSrcBelow ) {
+        if ( srcElemCount && srcElemCount <= unusedSrcBelow ) {
             return gddErrorOutOfBounds;
         }