Fixed issue where extra cursor was drawn in ImGui InputText field on TUI builds erroneously

[katemonster33]

Summary

Bugfixes "Fixes issue where the last typed character in an ImGui InputText field is covered by blank space on TUI/curses build"

Purpose of change

Fixes: #76129

Describe the solution

The IME Pre-Edit Text PR caused a regression on TUI/curses where some extra blank space is drawn on the screen. This was because of a typo where we were comparing a pointer on the stack to NULL, which will never be true. This instead checks if the first item in the array is NULL, this implies an empty string.

Describe alternatives you've considered

could have used ifdef TUI to block out pre-edit code entirely since none of it applies to curses, this just seemed simpler.

Testing

Before:
After:

Additional context

[akrieger]

NULL and '\0' are not definitionally the same. But imgui seems to use that convention.

[akrieger]

Wait nevermind, that's just the preedit text code.

Can you change these to use '\0' where we are talking about chars?

[akrieger]

Or like I'll do it after idgaf.

[katemonster33]

@akrieger done

[akrieger]

Is the pointer always guaranteed to be nonnull? Like this won't cause any null pointer dereferences right?

Edit: it's a preallocated array, nevermind.