Description of problem:
deleting a tag with backspace a caracter at a time.

Version-Release number of selected component:
Zim-0.58-1.fc17

Additional info:
libreport version: 2.0.18
abrt_version:   2.0.18
cmdline:        /usr/bin/python /usr/bin/zim --ipc-server-main /tmp/zim-rgouveia/zim-server-socket 30
kernel:         3.6.11-1.fc17.x86_64

backtrace:
:pageview.py:2069:set_tags:AssertionError: BUG: Tags should have a name
:
:Traceback (most recent call last):
:  File "/usr/lib/python2.7/site-packages/zim/gui/pageview.py", line 4248, in do_delete_range
:    tree = self.buffer.get_parsetree(bounds, raw=True)
:  File "/usr/lib/python2.7/site-packages/zim/gui/pageview.py", line 2096, in get_parsetree
:    set_tags(iter, filter(_is_zim_tag, iter.get_tags()))
:  File "/usr/lib/python2.7/site-packages/zim/gui/pageview.py", line 2069, in set_tags
:    assert attrib['name'], 'BUG: Tags should have a name'
:AssertionError: BUG: Tags should have a name
:
:Local variables in innermost frame:
:builder: <zim.formats.TreeBuilder object at 0x1fe4410>
:bullet: None
:tags: [<gtk.TextTag object at 0x27f94b0 (GtkTextTag at 0x223c240)>, <gtk.TextTag object at 0x27f9370 (GtkTextTag at 0x2701200)>]
:i: 0
:open_tags: [(<gtk.TextTag object at 0x27f94b0 (GtkTextTag at 0x223c240)>, 'div')]
:self: <TextBuffer object at 0x2014370 (zim+gui+pageview+TextBuffer at 0x21faa10)>
:iter: <GtkTextIter at 0x269d850>
:raw: True
:tag: <gtk.TextTag object at 0x27f9370 (GtkTextTag at 0x2701200)>
:t: 'tag'
:attrib: {'name': u''}
:continue_attrib: {}