[Patch] AbstractSTRtree::query segfaults if tree is empty

[framm]

If no items have been added to a tree, AbstractSTRtree::query() will execute an "intersects" call where one of the arguments is NULL, thus leading to a segmentation violation.

The expected behaviour of query() when querying an empty tree is to simply return an empty result.

Querying an empty tree might sound silly but if you're dealing with a larger system where the tree has been populated in another component you might not always know how many elements have been added, and the tree doesn't offer a public method like "isEmpty" or so.

The attached patch fixes the problem by immediately returning from query() if the tree is empty.

[framm]

Patch for AbstractSTRtree.cpp

[strk]

Ticket retargeted after milestone deleted

[strk]

Ticket retargeted after milestone closed

[strk]

Ticket retargeted after milestone closed

[dbaston]

Well, better late than never applying this: ​https://github.com/libgeos/geos/pull/116

framm, do you want to give your name for the commit log?

[Daniel Baston <dbaston@…>]

In ae8a2d31/git:

Avoid segfault when querying empty tree

Closes #730
Closes ​https://github.com/libgeos/geos/pull/116

[robe]

Looks like this was only applied to 3.7, were you going to apply to 3.6.4 or you think safer to just keep on 3.7?

[Daniel Baston <dbaston@…>]

In b0bff6d/git:

Avoid segfault when querying empty tree

Fixes #730