Capture eventual userland error handling tx error

Since the event handlers are run syncronously, if an `error` event handler thows, the error will return to the lib and keep the promise chain broken, rising an unhandled promise rejection error.

Resolves web3#3708

Author: gabmontes

packages/web3-core-method/src/index.js

@@ -729,7 +729,11 @@ Method.prototype.buildCall = function () {
                             .then(sendSignedTx)
                             .catch(function (err) {
                                 if (_.isFunction(defer.eventEmitter.listeners) && defer.eventEmitter.listeners('error').length) {
+                                    try {
                                     defer.eventEmitter.emit('error', err);
+                                    } catch (err) {
+                                        // Ignore userland error prevent it to bubble up within web3.
+                                    }
                                     defer.eventEmitter.removeAllListeners();
                                     defer.eventEmitter.catch(function () {
                                     });