Every KoShapeController used to reset the global "shape document" in its
KoDocumentResourceManager. The problem is that in Krita we have multiple
KoShapeController-s, but the resource manager is the only one. It means
that every shape selection or shape layer used to reset the pointer to
the global "shape document" to its own one. The only reason why we didn't
have too many crashes is that almost noone uses this "shape document".
Ideally we should:
1) Remove KoDocumentResourceManager::GlobalShapeController resource. This
resource is not global to the document, but is created per-layer. The only
user of it atm is the legacy text tool, which should be deprecated.
2) Remove KoDocumentResourceManager at all. There is no much use of it
anymore. Its main user is legacy text tool.