Fix missing error handling for IPC::Open3 in ipc_open3 subroutine

[prjanitor]

Description

The ipc_open3 subroutine in lib/MIP/System_call.pm did not check if open3() succeeds before attempting to read from filehandles. If open3() fails, $writer, $reader, and $error will be undefined, causing silent failures or crashes when reading from undefined filehandles.

Changes

• Added error handling after the open3() call to check if it succeeded
• If open3() fails (returns undef), the subroutine now croaks with an informative error message including the command string and the system error
• This prevents silent failures and makes debugging easier

Testing

The fix ensures that:

1. If open3() fails, an error is raised immediately with context
2. The filehandles are only accessed after confirming open3() succeeded
3. The error message includes the command that failed for easier debugging

Closes #431

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