[WORDPAD] Fix garbage in "Get Text" dialog (#7922)

This fixes the garbage in the "Get Text" dialog which occurs if there is no text input
and one clicks on "Get Text" under Extras.

CORE-19868
Reported to Wine: https://bugs.winehq.org/show_bug.cgi?id=58144

base/applications/wordpad/wordpad.c

@@ -2294,6 +2294,9 @@ static LRESULT OnCommand( HWND hWnd, WPARAM wParam, LPARAM lParam)
         tr.chrg.cpMax = nLen;
         tr.lpstrText = data;
         SendMessageW(hwndEditor, EM_GETTEXTRANGE, 0, (LPARAM)&tr);
+#ifdef __REACTOS__
+        data[tr.chrg.cpMax - tr.chrg.cpMin] = UNICODE_NULL;
+#endif
         MessageBoxW(NULL, data, wszAppTitle, MB_OK);
         HeapFree( GetProcessHeap(), 0, data );