Critical warning when grouping/ungrouping a filtered object (rev >= 13824)

[su_v]

Recent trunk builds emit critical warnings on the console whenever a filtered objects is grouped, or a group containing a filtered object (possibly deeply within nested groups) is ungrouped. The same messages are generated if a clone of such an object is grouped/ungrouped or deleted.

Steps to reproduce:
1) launch trunk (default new prefs, default new doc)
2) draw a rect
3) blur it (or apply one of the preset filters)
4a) group it, ungroup it (or group it again)
4b) clone it, group the clone
4c) clone it, delete clone

Console message(s):
** (inkscape:13451): CRITICAL **: void SPObject::requestModified(unsigned int): assertion 'this->document != NULL' failed

Reproduced with Inkscape 0.91+devel r14390 on OS X 10.7.5.

Based on tests with archived builds:
- not reproduced with rev <= 13822,
- reproduced with rev >= 13824;
the critical warnings might be related to changes in r13824:
Revision 13824: "Replace sp_style_xxx functions with SPStyle member functions.
Fix a bunch of memory leaks. One leak still remaining in Layout::appendText."
https://bazaar.launchpad.net/~inkscape.dev/inkscape/trunk/revision/13824

[jazzynico (jazzynico)]

Reproduced on Xubuntu 15.04, Inkscape trunk rev. 14392.

[jazzynico (jazzynico)]

The error seems to occur when SPObject::requestModified (in src/sp-object.cpp:1166) is called from sp_style_filter_ref_modified (in src/sp-style.cpp:1284) with an object that was already released (tested in debug mode, with some additional code, and the object's ID is the same in SPObject::release and in SPObject::requestModified):

----
/home/nicolas/dev/bzr/inkscape/trunk/src/sp-object.cpp(612) release:id=0x5d4ed10, typename=(null)

** (inkscape:23048): WARNING **: entering 'sp_style_filter_ref_modified'
/home/nicolas/dev/bzr/inkscape/trunk/src/sp-object.cpp(1168) requestModified:id=0x5d4ed10, typename=(null)

** (inkscape:23048): CRITICAL **: void SPObject::requestModified(unsigned int): assertion 'this->document != NULL' failed
----