Application crashes on right-click in empty Project Explorer space

[nayifus]

Steps to Reproduce

1. Start the application
2. Open the Project Explorer panel
3. Right-click on an empty region (no file/folder selected)

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Expected Behavior

The application should continue running normally. It should either do nothing or display a basic context menu.

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Actual Behavior

Right-clicking without any selected item causes the application to crash.

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Environment

• eSim version: Latest (master)
• OS: Windows (64-bit)

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Cause

The current implementation of the context menu depends on selectedIndexes() and assumes that a selection is always present.
When the selection is empty:

• Attempting to access the first index results in an error
• Some dependent variables may not get assigned properly

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Suggested Fix

Instead of relying on selection, determine the clicked item using indexAt(position) and verify it with index.isValid() before using it.
This ensures safe handling of clicks on empty areas.