Handle path state on Explore unmount

[viveknigam3003]

Motivation

The path for Explorer is stored and accessed from the state tree which works fine when browsing the scoped namespace. BUT, the application does not handle unexpected unmount of the Explore tab component, which causes the app to crash.

Error Log:

Error: EIO: i/o error, stat '/ruciofs/rucio-server-x509/test/dataset3/rucio-server-x509'
[1]     at Object.statSync (fs.js:933:3)
[1]     at getFiles (/home/vivek/Desktop/GSoC_2020/desktop/server/APIs/files.js:23:10)
[1]     at /home/vivek/Desktop/GSoC_2020/desktop/server/routes/files.js:16:16
[1]     at Layer.handle [as handle_request] (/home/vivek/Desktop/GSoC_2020/desktop/node_modules/express/lib/router/layer.js:95:5)
[1]     at next (/home/vivek/Desktop/GSoC_2020/desktop/node_modules/express/lib/router/route.js:137:13)
[1]     at Route.dispatch (/home/vivek/Desktop/GSoC_2020/desktop/node_modules/express/lib/router/route.js:112:3)
[1]     at Layer.handle [as handle_request] (/home/vivek/Desktop/GSoC_2020/desktop/node_modules/express/lib/router/layer.js:95:5)
[1]     at /home/vivek/Desktop/GSoC_2020/desktop/node_modules/express/lib/router/index.js:281:22
[1]     at Function.process_params (/home/vivek/Desktop/GSoC_2020/desktop/node_modules/express/lib/router/index.js:335:12)
[1]     at next (/home/vivek/Desktop/GSoC_2020/desktop/node_modules/express/lib/router/index.js:275:10)

Modification

Fix the unmount handling by adding a cleaup effect for component unmount, and resets the path state on unmount.

Expected Results

• The app handles unexpected clicking of any other tab.
• Path state cleaned and reset on opening some other tab or selecting some other function.