CopyQ unable to correctly identify specific character patterns (e.g. CRLF)

**Describe the bug**
CopyQ appears to have challenges correctly identifying specific character patterns. Specifically, a `CRLF` sequence, optionally appended by a null.

**To Reproduce**
1. Import this CopyQ command:
```
[Command]
Name=Ignore CRLF/LF if Sole Content
Match=^\\r?\\n\\x00?$
Automatic=true
Remove=true
Icon=
```

2. Copy a `CRLF` character sequence to the clipboard.
3. Notice that CopyQ doesn't completely ignore it; a notification pops up indicating that 2 lines were copied to the clipboard. On the other hand, an empty item is not created in CopyQ's clipboard history list.
4. Change the command's regex to `.*`
5. Copy anything to the clipboard.
6. Copy a `CRLF` to the clipboard.
7. Same result as 3.

**Expected behavior**
CopyQ to ignore when user tries to copy only an `LF` or `CRLF`, optionally appended by a null.

**Version, OS and Environment**
```
CopyQ 16.0.0
Arch: x86_64-little_endian-llp64
Audio: miniaudio 0.11.25
Compiler: MSVC
KNotifications: 6.23.0
KStatusNotifierItem: 6.23.0
OS: Windows 11 Version 25H2
QCA: 2.3.10
Qt: 6.10.2
QtKeychain: 0.15.0
has-audio: 1
has-encryption: 1
has-global-shortcuts: 1
has-keychain: 1
has-mouse-selection: 0
```

**Additional context**
I use a couple tools that will copy an `LF` or `CRLF` to the clipboard when nothing is selected (one of them appends a `null` afterwards too). This usually occurs when I accidentally press Ctrl+C instead of Ctrl+V to perform a paste operation. Instead of removing the contents of the clipboard and issuing a confusing notification, I would like CopyQ to leave the clipboard unchanged. Ideally, I would also like CopyQ to display an "Empty string not copied to clipboard" notification.

Start by reproducing the issue with the imported command using `^\\r?\\n\\x00?$`, then compare it with `.*` as described. Trace CopyQ's handling of clipboard text, regex matching, removal, and notifications for LF/CRLF content. Done means LF or CRLF, optionally followed by a null, leaves the existing clipboard unchanged and reports the expected empty-string behavior.

Written by the indexing model from the issue text.