selenium IDE module 10 creating own commands

while creating new commands in user-extensions.js in selenium IDE module 10 and trying to execute the test case it throws an error saying




[info] Playing test case Untitled
[info] Executing: |generateRandomEmail | | |
[error] Unexpected Exception: [Exception... "Component does not have requested interface" nsresult: "0x80004002 (NS_NOINTERFACE)" location: "JS frame :: chrome://selenium-ide/content/tools.js -> file:///C:/XMLFiles/sideflow-master/user-extensions.js?1450720138000 :: Selenium.prototype.doGenerateRandomEmail :: line 123" data: no]. toString -> function toString() {
[native code]
}, message -> , result -> 2147500034, name -> NS_NOINTERFACE, filename -> chrome://selenium-ide/content/tools.js -> file:///C:/XMLFiles/sideflow-master/user-extensions.js?1450720138000, lineNumber -> 123, columnNumber -> 0, inner -> null, data -> null, stack -> Selenium.prototype.doGenerateRandomEmail@chrome://selenium-ide/content/tools.js -> file:///C:/XMLFiles/sideflow-master/user-extensions.js?1450720138000:123:1
fnBind/retval@chrome://selenium-ide/content/selenium-core/scripts/htmlutils.js:60:12
ActionHandler.prototype.execute@chrome://selenium-ide/content/selenium-core/scripts/selenium-commandhandlers.js:314:28
._executeCurrentCommand@chrome://selenium-ide/content/selenium-runner.js:306:19
TestLoop.prototype.resume@chrome://selenium-ide/content/selenium-core/scripts/selenium-executionloop.js:78:13
fnBind/retval@chrome://selenium-ide/content/selenium-core/scripts/htmlutils.js:60:12
, location -> JS frame :: chrome://selenium-ide/content/tools.js -> file:///C:/XMLFiles/sideflow-master/user-extensions.js?1450720138000 :: Selenium.prototype.doGenerateRandomEmail :: line 123
[info] Test case failed

Request you to please help