Descriptive Problem Summary: When the map editor is in Classic instancing mode, if two full-tile, identical turfs share the same location, using the Move/select tool to select any instance of that turf will result in a crash.

Numbered Steps to Reproduce Problem:
1) Download the following test project: http://files.byondhome.com/Higoten/Tests/ Map%20Selection%20Crash.zip
2) Open the map.dmm file and select Classic instancing mode.
3) Using the Move/select tool, select any black colored turf.
4) Observe that Dream Maker has crashed.

Test Project Notes:
In the project provided, the turfs located at 5, 9, 1 (North of the blue three) are important and directly related to the issue. There are two turfs of the same type with the same icon and icon_state, which can be verified though the context menu. Removing the topmost one resolves the issue. This generally does not occur as the map editor removes turf underlays that are not visible. In the test project, this situation occurred by creating a new instance with a non-full-tile icon_state that was placed on the target turf, followed by manually reverting its icon_state. The editor does not recognize them as being the same instance unless Reset to default was used.

Expected Results: For Dream Maker not to crash.

Actual Results: When any instance of the identical, underlaid turfs is selected, Dream Maker crashes while in Classic instancing mode.

Does the problem occur:
Every time? Or how often? Every time.

When does the problem NOT occur? The problem does not occur in Copy instancing mode.

Workarounds: Delete the offending turfs.