txdb: fix assert.

lib/wallet/txdb.js

@@ -1470,13 +1470,6 @@ TXDB.prototype.disconnect = co(function* disconnect(tx) {
 
     credit = yield this.getCredit(hash, i);
 
-    assert(credit);
-    assert(!credit.spent);
-
-    // Neither of the spent cases below
-    // should ever happen, but account
-    // for them if some jackass is messing
-    // around with bcoin.
     if (!credit) {
       yield this.updateSpentCoin(tx, i);
       continue;