Remove error message that couldn't be displayed anyway [fixes #955]

@zolotov or @ignatov if you guys have a better idea, please let me know. Thanks.

@mtoader I leave this up to you but I'd rather have one of the guys having a look on this one, maybe we can have a better solution for it.

The full error that happens otherwise is:
```java

[   6636]  ERROR - ellij.openapi.ui.DialogWrapper - Dialog must be init in EDT only: Thread[ApplicationImpl pooled thread 4,4,main] 
java.lang.Throwable
	at com.intellij.openapi.diagnostic.Logger.error(Logger.java:115)
	at com.intellij.openapi.ui.DialogWrapper.init(DialogWrapper.java:1165)
	at com.intellij.openapi.ui.Messages$MessageDialog._init(Messages.java:1391)
	at com.intellij.openapi.ui.Messages$MessageDialog.<init>(Messages.java:1358)
	at com.intellij.openapi.ui.Messages.showDialog(Messages.java:278)
	at com.intellij.openapi.ui.Messages.showDialog(Messages.java:291)
	at com.intellij.openapi.ui.Messages.showDialog(Messages.java:302)
	at com.intellij.openapi.ui.Messages.showErrorDialog(Messages.java:739)
	at ro.redeul.google.go.ide.GoGlobalConfigurableForm.populateFromSDKs(GoGlobalConfigurableForm.java:63)
	at ro.redeul.google.go.ide.GoGlobalConfigurableForm.<init>(GoGlobalConfigurableForm.java:53)
	at ro.redeul.google.go.ide.GoGlobalConfigurable.createComponent(GoGlobalConfigurable.java:47)
	at com.intellij.openapi.options.ex.ConfigurableWrapper.createComponent(ConfigurableWrapper.java:162)
	at com.intellij.openapi.options.newEditor.OptionsEditor$Simple.<init>(OptionsEditor.java:1052)
	at com.intellij.openapi.options.newEditor.OptionsEditor.initConfigurable(OptionsEditor.java:507)
	at com.intellij.openapi.options.newEditor.OptionsEditor.access$1900(OptionsEditor.java:67)
	at com.intellij.openapi.options.newEditor.OptionsEditor$9$1$1.run(OptionsEditor.java:476)
	at com.intellij.openapi.application.impl.ApplicationImpl.runEdtSafeAction(ApplicationImpl.java:1090)
	at com.intellij.openapi.options.newEditor.OptionsEditor$9$1.run(OptionsEditor.java:469)
	at com.intellij.openapi.application.impl.ApplicationImpl.runReadAction(ApplicationImpl.java:905)
	at com.intellij.openapi.options.newEditor.OptionsEditor$9.run(OptionsEditor.java:466)
	at com.intellij.openapi.application.impl.ApplicationImpl$8.run(ApplicationImpl.java:405)
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
	at java.util.concurrent.FutureTask.run(FutureTask.java:266)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
	at java.lang.Thread.run(Thread.java:745)
	at org.jetbrains.ide.PooledThreadExecutor$1$1.run(PooledThreadExecutor.java:56)
[   6641]  ERROR - ellij.openapi.ui.DialogWrapper - IntelliJ IDEA (Community Edition) IC-139.SNAPSHOT  Build #IC-139.SNAPSHOT 
[   6641]  ERROR - ellij.openapi.ui.DialogWrapper - JDK: 1.8.0_25 
[   6641]  ERROR - ellij.openapi.ui.DialogWrapper - VM: Java HotSpot(TM) 64-Bit Server VM 
[   6641]  ERROR - ellij.openapi.ui.DialogWrapper - Vendor: Oracle Corporation 
[   6641]  ERROR - ellij.openapi.ui.DialogWrapper - OS: Linux 
[   6641]  ERROR - ellij.openapi.ui.DialogWrapper - Last Action: ShowSettings 
[   6663]  ERROR - plication.impl.ApplicationImpl - The DialogWrapper can be used only on event dispatch thread. 
java.lang.IllegalStateException: The DialogWrapper can be used only on event dispatch thread.
	at com.intellij.openapi.ui.DialogWrapper.ensureEventDispatchThread(DialogWrapper.java:1998)
	at com.intellij.openapi.ui.DialogWrapper.showAndGetOk(DialogWrapper.java:1553)
	at com.intellij.openapi.ui.DialogWrapper.show(DialogWrapper.java:1536)
	at com.intellij.openapi.ui.Messages$MessageDialog.show(Messages.java:1478)
	at com.intellij.openapi.ui.Messages.showDialog(Messages.java:279)
	at com.intellij.openapi.ui.Messages.showDialog(Messages.java:291)
	at com.intellij.openapi.ui.Messages.showDialog(Messages.java:302)
	at com.intellij.openapi.ui.Messages.showErrorDialog(Messages.java:739)
	at ro.redeul.google.go.ide.GoGlobalConfigurableForm.populateFromSDKs(GoGlobalConfigurableForm.java:63)
	at ro.redeul.google.go.ide.GoGlobalConfigurableForm.<init>(GoGlobalConfigurableForm.java:53)
	at ro.redeul.google.go.ide.GoGlobalConfigurable.createComponent(GoGlobalConfigurable.java:47)
	at com.intellij.openapi.options.ex.ConfigurableWrapper.createComponent(ConfigurableWrapper.java:162)
	at com.intellij.openapi.options.newEditor.OptionsEditor$Simple.<init>(OptionsEditor.java:1052)
	at com.intellij.openapi.options.newEditor.OptionsEditor.initConfigurable(OptionsEditor.java:507)
	at com.intellij.openapi.options.newEditor.OptionsEditor.access$1900(OptionsEditor.java:67)
	at com.intellij.openapi.options.newEditor.OptionsEditor$9$1$1.run(OptionsEditor.java:476)
	at com.intellij.openapi.application.impl.ApplicationImpl.runEdtSafeAction(ApplicationImpl.java:1090)
	at com.intellij.openapi.options.newEditor.OptionsEditor$9$1.run(OptionsEditor.java:469)
	at com.intellij.openapi.application.impl.ApplicationImpl.runReadAction(ApplicationImpl.java:905)
	at com.intellij.openapi.options.newEditor.OptionsEditor$9.run(OptionsEditor.java:466)
	at com.intellij.openapi.application.impl.ApplicationImpl$8.run(ApplicationImpl.java:405)
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
	at java.util.concurrent.FutureTask.run(FutureTask.java:266)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
	at java.lang.Thread.run(Thread.java:745)
	at org.jetbrains.ide.PooledThreadExecutor$1$1.run(PooledThreadExecutor.java:56)

```