Crash converting text with empty first tspan to path (rev >= 14066)

[su_v]

Current Inkscape trunk crashes when converting a multi-line regular text object to path which has an empty first line (<tspan>).

Steps to reproduce:
1) launch current trunk (default new prefs, default new doc)
2) switch to text tool
3) click once on the canvas
4) create empty first line (<Return>)
5) type a word on the second line
6) switch to select tool
7) convert text to path

--> inkscape crashes:
Program received signal EXC_BAD_ACCESS, Could not access memory.
Reason: KERN_INVALID_ADDRESS at address: 0x0000000000000000
0x0000000101fd0530 in Glib::get_unichar_from_std_iterator ()
(gdb) bt
#0 0x0000000101fd0530 in Glib::get_unichar_from_std_iterator ()
#1 0x000000010009184d in sp_selected_item_to_curved_repr ()
#2 0x0000000100090727 in sp_item_list_to_curves ()
#3 0x00000001000912ee in sp_selected_path_to_curves ()
#4 0x0000000100188e29 in Inkscape::ObjectVerb::perform ()
#5 0x0000000100026a0a in sigc::internal::signal_emit0<void, sigc::nil>::emit ()
#6 0x00000001002cc023 in sp_action_perform ()
#7 0x00000001033a1e29 in g_closure_invoke ()
#8 0x00000001033b4737 in signal_emit_unlocked_R ()
#9 0x00000001033b572c in g_signal_emit_valist ()
#10 0x00000001033b5a9a in g_signal_emit ()
#11 0x0000000101993fe8 in gtk_widget_activate ()
#12 0x00000001018aa6cd in gtk_menu_shell_activate_item ()
#13 0x00000001018ab0a1 in gtk_menu_shell_button_release ()
#14 0x000000010189aea8 in _gtk_marshal_BOOLEAN__BOXED ()
#15 0x00000001033a1e29 in g_closure_invoke ()
#16 0x00000001033b48ab in signal_emit_unlocked_R ()
#17 0x00000001033b578f in g_signal_emit_valist ()
#18 0x00000001033b5a9a in g_signal_emit ()
#19 0x0000000101993de1 in gtk_widget_event_internal ()
#20 0x000000010189919c in gtk_propagate_event ()
#21 0x0000000101898e11 in gtk_main_do_event ()
#22 0x0000000101c3c6ed in gdk_event_dispatch ()
#23 0x00000001034134b7 in g_main_context_dispatch ()
#24 0x0000000103413778 in g_main_context_iterate ()
#25 0x00000001034139fd in g_main_loop_run ()
#26 0x0000000101898796 in gtk_main ()
#27 0x0000000100002fc5 in sp_main_gui ()
#28 0x0000000100002434 in start ()

First encountered with Inkscape 0.91+devel r14389 on OS X 10.7.5.

Based on tests with archived builds:
- not reproduced with rev <= 14063,
- reproduced with rev >= 14066;
this crash is likely exposed by the changes in r14066:
Revision 14066: Save original text in 'aria-label' attribute for accessibilty reasons.
https://bazaar.launchpad.net/~inkscape.dev/inkscape/trunk/revision/14066

Variation:
- crash is also triggered if first line contains spaces (in step 4, type a few spaces before the newline).

[Tavmjong Bah (tavmjong-free)]

Should be fixed in r14390.

[su_v (suv-lp)]

Fix confirmed with Inkscape 0.91+devel r14390 on OS X 10.7.5.

Thanks a lot!