Print error message when available

With the current set up, error message is only printed out when error name is available.
There are situations where the ErrorEvent object does not have a `name` property, but the message is still relevant.

For more details see #1594

src/core/ExceptionFormatter.js

@@ -7,6 +7,8 @@ getJasmineRequireObj().ExceptionFormatter = function(j$) {
 
       if (error.name && error.message) {
         message += error.name + ': ' + error.message;
+      } else if (error.message) {
+        message += error.message;
       } else {
         message += error.toString() + ' thrown';
       }