Database: Warn about inconsistent database state.

lib/services/db.js

@@ -122,6 +122,10 @@ DB.prototype.start = function(callback) {
     } else {
       self.getBlock(metadata.tip, function(err, tip) {
         if(err) {
+          log.warn(
+            'Database is in an inconsistent state, a reindex is needed. Could not get current tip:',
+            metadata.tip
+          );
           return callback(err);
         }
         self.tip = tip;