Fixes: you specified keyIsUint32 on the Dbi

Fixes bug where height < 0 and causes error on line 43: `Error: You specified keyIsUint32 on the Dbi, so you can't use other key types with it.`

lib/worker.js

@@ -127,7 +127,7 @@ function updateShareStats() {
             }, function (oldestTime) {
                 height -= 1;
                 loopBreakout += 1;
-                if (loopBreakout > 60) {
+                if (loopBreakout > 60 || height < 0) {
                     return true;
                 }
                 return oldestTime <= identifierTime;
@@ -534,4 +534,4 @@ setInterval(updatePoolStats, 5000, 'pps');
 setInterval(updatePoolStats, 5000, 'solo');
 setInterval(updatePoolInformation, 5000);
 setInterval(updateWalletStats, 60000);
-setInterval(monitorNodes, 300000);
+setInterval(monitorNodes, 300000);