Added check for missing header.

lib/blocks.js

@@ -211,11 +211,20 @@ BlockController.prototype._getBlockSummary = function(hash, moreTimestamp, next)
 
       var block = bcoin.block.fromRaw(blockBuffer, 'hex');
 
+      // if we don't we a block header back, this is highly unusual,
+      // but possible if there was a very recent reorg and the header
+      // was removed but the block was not yet removed from the index.
+      // It is best to not return a result.
       self._header.getBlockHeader(hash, function(err, header) {
 
         if (err) {
           return next(err);
         }
+
+        if (!header) {
+          return next();
+        }
+
         var height = header.height;
 
         var summary = {