Skype add-on installed on FF is responsible for the same issue. Uninstall Skype Click to Call(~7.2MB File) software from Control Panel.
Please try this
String originalHandle = driver.getWindowHandle();
//Do something to open new tabs
for(String handle : driver.getWindowHandles()) {
if (!handle.equals(originalHandle)) {
driver.switchTo().window(handle);
driver.close();
}
}