Surface Snapping window does not clear search option when window closes

When the viewport Surface Snapping window has focus and text is entered, it will use the text as search keywords. When the window is closed, the text is not cleared the next time the window is opened.

Workaround:
When the window is reopened, specifically clicking in the window will allow the text to be deleted manually.

Regression:
No - same behavior occurs in 4.15.3 Binary

1. Open UE4 Editor (any project)
2. Click the button to "Open editor surface snapping options" in the top right of the viewport (fifth icon from the left)
3. Click "Settings" to give the window focus and enter text
4. Close the window by clicking anywhere in the viewport then reopen the window

Result:
Window is still searching for entered text

Expected:
When the window is reopened, default window options appear.