Bug: To fix a NullPointerException in ShareDataActivity

[radcolor]

• Description
  In ShareDataActivity we checking if appDir.listFiles() != null to continue our work. Though in L68 we trying to get the length of our File array fileList = new String[files.length] without even checking if our array is null or not and that can lead to Crash and Runtime exception if array found null, and can lead to poor user experience

• Expected Behavior
  If the our CSV dir doesn't exist then no need to call ShareDataActivity, either we can check for the csv file list before calling it in NeuroLab.java on method onNavigationItemSelected() or either to get array length of file after confirming that our array is not null and if found null then show a message to user that our file doesn't exist/no data to share!

• Steps to reproduce it
  If our CSV dir is empty or file are null, then ShareDataActivity will crash because of null array

• System Information

Device	Xiaomi Redmi Note 5 Pro/AI (whyred)
Android version/OS	Android Q (API 29)

I'll provide a runtime crash screenshot below! I can have a PR over here to fix this!

[jddeep]

Go ahead!

[pratik9315]

Hello sir, can I work on this issue?