Fix bug with getting a block index with unknown height.

integration/regtest.js

@@ -184,6 +184,14 @@ describe('Daemon Binding Functionality', function() {
         });
       });
     });
+
+    it('will get error with number greater than tip', function(done) {
+      bitcoind.getBlock(1000000000, function(err, response) {
+        should.exist(err);
+        done();
+      });
+    });
+
   });
 
   describe('get transactions by hash', function() {
@@ -254,6 +262,11 @@ describe('Daemon Binding Functionality', function() {
         blockIndex.height.should.equal(i);
       });
     });
+    it('will get null with number greater than tip', function(done) {
+      var index = bitcoind.getBlockIndex(100000);
+      should.equal(index, null);
+      done();
+    });
   });
 
   describe('isMainChain', function() {

src/libbitcoind.cc

@@ -1267,6 +1267,7 @@ NAN_METHOD(GetBlockIndex) {
 
     if (blockIndex == NULL) {
       info.GetReturnValue().Set(Null());
+      return;
     }
 
   } else {