Fixed listenerCount for contract when requesting for all events (#1205).

Author: ricmoo

packages/contracts/src.ts/index.ts

@@ -1016,6 +1016,11 @@ export class Contract {
 
     listenerCount(eventName?: EventFilter | string): number {
         if (!this.provider) { return 0; }
+        if (eventName == null) {
+            return Object.keys(this._runningEvents).reduce((accum, key) => {
+                return accum + this._runningEvents[key].listenerCount();
+            }, 0);
+        }
         return this._getRunningEvent(eventName).listenerCount();
     }