bug#21738: 25.0.50; eww freezes/crashes at times

[Kaushal Modi]

Here is another backtrace for the same freeze issue (attached).

This time it was causing by doing C-x C-f of png files twice in the same buffer.

Here's how to recreate:

1. cd to src/ dir
2. gdb ./emacs
3. r -Q
4. C-x C-f SOMEFILE1.png (emacs has not frozen yet)
5. C-x C-f SOMEFILE2.png (emacs freezes instantly)

===========================================

Built on x86_64-unknown-linux-gnu
Configure options:
--prefix=/home/kmodi/usr_local/apps/6/emacs/master_debug
'CPPFLAGS=-fgnu89-inline -I/home/kmodi/usr_local/6/include
-I/usr/include/freetype2 -I/usr/include' 'CFLAGS=-ggdb3 -O0'
'CXXFLAGS=-ggdb3 -O0' 'LDFLAGS=-L/home/kmodi/usr_local/6/lib
-L/home/kmodi/usr_local/6/lib64 -ggdb3'
Features: XPM JPEG TIFF GIF PNG RSVG IMAGEMAGICK SOUND GPM DBUS GCONF
GSETTINGS NOTIFY ACL LIBSELINUX GNUTLS LIBXML2 FREETYPE LIBOTF XFT
ZLIB TOOLKIT_SCROLL_BARS GTK2 X11

emacs_25_Imagemagick_png_open_freeze_gdb_bt.log
Description: Binary data