bug#22575: 25.0.50; isearch-query-replace wrong type argument

[Óscar Fuentes]

emacs -Q

In *scratch*, put the point at the beginning of the buffer and

M-x isearch-query-replace

The minibuffer shows

Wrong type argument: stringp, nil

The same happens if an isearch was previously executed. (From reading
the docstring, I don't know how isearch-query-replace is supposed to
work.)

In GNU Emacs 25.0.50.29 (x86_64-unknown-linux-gnu, X toolkit)
 of 2016-01-21 built on qcore
Repository revision: 5293d1bdb3e665a565af032a163004c976328cc2
Windowing system distributor 'The X.Org Foundation', version 11.0.11702000
System Description:     Ubuntu 15.10

Configured using:
 'configure --without-toolkit-scroll-bars --with-x-toolkit=lucid'

Configured features:
XAW3D XPM JPEG TIFF GIF PNG SOUND GSETTINGS NOTIFY GNUTLS LIBXML2
FREETYPE XFT ZLIB LUCID X11

Important settings:
  value of $LANG: C
  locale-coding-system: nil

Major mode: Emacs-Lisp