Flashtool not running topic

Hi can anyone help me with this error please?

java.lang.NullPointerException
at gui.MainSWT.createContents(MainSWT.java:660)
at gui.MainSWT.open(MainSWT.java:109)
at gui.Main.main(Main.java:36)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Nativ e Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknow n Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Un known Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at com.exe4j.runtime.LauncherEngine.launch(Unknown Source)
at com.exe4j.runtime.WinLauncher.main(Unknown Source)

I can´t execute the flashtool... What's wrong? I want to downgrade my Xperia Z1 and I can't because I can't make the program run!

Thanks in advance guys :)