Crash/Leak when deleting datatip

Reported by Caio SOUZA

BUG DESCRIPTION:
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1)Deleting a datatip from a loaded *.scg file and closing the figure leads to crash;
2)Using the "datatipRemove" macro with invalid index leads to crash
3)Datatip graphic object were not deleted when its parent polyline was deleted.



ERROR LOG:
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HOW TO REPRODUCE THE BUG:
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1)//Test case
param3d();
e=gce();
datatipCreate(e, 2);
fname = TMPDIR + '/datatip_crash_test.scg'
xsave(fname);
close(gcf());
load(fname);
deletefile(fname);
e=gce();
p=e.children;
datatipRemove(p, 1);
close(gcf());

2)//Test case

param3d();
e=gce();
datatipCreate(e, 2);
datatipRemove(e, 10)

3)//Test case
param3d();
e=gce();
d=datatipCreate(e, 2);
delete(e);
assert_checkequal(is_handle_valid(d), %F)

OTHER INFORMATION:
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