Single-character search query is accepted but not matched

[fubai578]

Checklist

• I can reproduce the bug with the latest version given here.
• I made sure that there are no existing issues - open or closed - to which I could contribute my information.
• I made sure that there are no existing discussions - open or closed - to which I could contribute my information.
• I have read the FAQs inside the app (Menu -> About -> FAQs) and my problem isn't listed.
• I have taken the time to fill in all the required details. I understand that the bug report will be dismissed otherwise.
• This issue contains only one bug.
• I have read and understood the contribution guidelines.

Affected app version

### Affected Android/Custom ROM version

Android 14 (API 34)

### Affected device model

MuMu Android Emulator (900 x 1600)

### How did you install the app?

F-Droid / IzzyOnDroid

### Steps to reproduce the bug

1. Create a note containing `aXbX`.
2. Open Search in the note and enter the single character `X`.
3. For comparison, enter `aX` in the same note.

### Expected behavior

The non-empty one-character query should locate the `X` matches, or the app should clearly reject such queries.

### Actual behavior

The query `X` stays in the search box but produces no match indication, while `aX` highlights its matches in the same note. Nothing tells me the one-character query is unsupported.

### Screenshots/Screen recordings

<img width="900" height="1600" alt="Image" src="https://github.com/user-attachments/assets/1a6c0cc1-a4a5-470d-bad6-addf02c899b7" />

<img width="900" height="1600" alt="Image" src="https://github.com/user-attachments/assets/0b793212-50fd-446f-b475-33aa97cd9d72" />

<img width="900" height="1600" alt="Image" src="https://github.com/user-attachments/assets/8068f410-dca1-464a-a119-fe1814973334" />

### Additional information

- Package: `org.fossify.notes`
- Tested version: 1.7.0 (version code 13)
- Environment: Android 14 (API 34), MuMu Android Emulator (900 x 1600)

Searching a single letter is the most natural thing to type, and silently doing nothing feels like the search is broken.