[CharInv] Modifiers don't always show up in the find-and-replace fields

[imnasnainaec]

Describe the bug

Some combining characters don't stand on their own but modify a neighboring character.

To Reproduce

1. In Data Entry, add a word with the following Arabic for the Vernacular form: اَلْعَرَبِيَّةُ
2. Click on Data Cleanup, then Create Character Inventory
3. Select the card for one of the modifiers (U+064E through U+0652)
4. Find the "FIND & REPLACE" panel (right for wide windows, bottom for narrow windows)
5. Observe that the "Find" text-field seams to be empty
6. Click in the field, press the spacebar, and see the character appear

NOTE: Wait for user requests before defining the solution requirements

[imnasnainaec]

Related: #1581