System should correctly report that it can't open target pptx because it protected by password

[AlexeyGirin]

Steps to Reproduce
Try on both - Stand Alone version and on Remote version

1. Click Open... button (Ctrl+O)
2. Select open from file
3. Select file: PasswordProtected.pptx
4. Click Open

Actual behavior
System reports: No embedded structures found in the file

Expected behavior
System detects that file is password protected and ask user to remove it if it wants to load molecules from it

Environment details:

• Ketcher Version 2.18.0-rc.6 Build at 2024-02-13; 19:05:50
• Indigo Toolkit Version 1.18.0-rc.7.0-g8a5c36802-wasm32-wasm-clang-12.0.0
• Chrome Version 121.0.6167.185 (Official Build) (64-bit)
• Win10
• Issue found while testing Add support for opening structures in CDX format embedded into MS PowerPoint #3914

[AlexeyGirin]

Correct error message (report that we can't open it - may be it is password protected)