Don't try to access a bogus read if no overlaps exist.

src/correction/generateCorrectionLayouts.C

@@ -367,19 +367,21 @@ main(int argc, char **argv) {
     uint32   readID = (ovlLen > 0) ? ovl[0].a_iid : UINT32_MAX;   //  Read ID of overlaps, or maximum ID if no overlaps.
     tgTig   *layout = new tgTig;
 
-    layout->_tigID           = ii;
-    layout->_layoutLen       = gkpStore->gkStore_getRead(readID)->gkRead_sequenceLength();
+    layout->_tigID = ii;
 
     assert(ii <= readID);
 
     //  If ii is below readID, there are no overlaps for this read.  Make an empty placeholder tig for it.
     //  But if ii is readID, we have overlaps, so process them, then load more.
 
     if (ii == readID) {
+      layout->_layoutLen = gkpStore->gkStore_getRead(readID)->gkRead_sequenceLength();
+
       layout = generateLayout(layout,
                               olapThresh,
                               minEvidenceLength, maxEvidenceErate, maxEvidenceCoverage,
                               ovl, ovlLen);
+
       ovlLen = ovlStore->readOverlaps(ovl, ovlMax, true);
     }