fix: validation returns illegal state error

[mateuszjenek]

This PR simply ignores illegal state - object is disposed as it occurred when the object (in this example document) is already disposed.

[ERROR] {"message":"illegal state - object is disposed","stack":"Error: illegal state - object is disposed\n    at Q3.j (file:///Applications/Visual%20Studio%20Code.app/Contents/Resources/app/out/vs/workbench/api/node/extensionHostProcess.js:137:95055)\n    at Q3.set (file:///Applications/Visual%20Studio%20Code.app/Contents/Resources/app/out/vs/workbench/api/node/extensionHostProcess.js:137:93515)\n    at ValidateScoreFileController.validate (/Users/mjenek/.vscode/extensions/humanitec.humanitec-0.2.3/out/controllers/ValidateScoreFileController.js:154:30)\n    at /Users/mjenek/.vscode/extensions/humanitec.humanitec-0.2.3/out/controllers/ValidateScoreFileController.js:90:21","name":"Error"}