org.eclipse.swt.SWTException: Failed to execute runnable (java.lang.IllegalArgumentException: Argument cannot be null)

This exception indicates that an argument passed to a method in the SWT (Standard Widget Toolkit) library is null, which is not allowed.

To resolve this issue, you need to identify the method that is throwing this exception and ensure that all the arguments passed to it are not null. You can do this by checking the code that is executing when the exception occurs and tracing it back to the method that is causing the problem.

Once you have identified the method, you can check its documentation to see which arguments are required and ensure that you are passing valid values for them. You may also need to add some null checks in your code to prevent this exception from occurring.

Overall, this exception is often caused by programming errors, such as forgetting to initialize a variable or passing null to a method that does not allow it. Therefore, it is important to carefully review your code and ensure that all arguments are properly initialized and passed to methods.