Fix slicing with negative indices

Negative indices that remained negative after adding the sequence length
caused incorrect slicing.

With the default scene for example:

   bpy.context.scene.objects[-4:2]

Gave a different result to:

   tuple(bpy.context.scene.objects)[-4:2]

Clamp indices above zero so loops that step forward works as intended.

1 files changed, 2 insertions, 0 deletions

diff --git a/source/blender/python/bmesh/bmesh_py_types_select.c b/source/blender/python/bmesh/bmesh_py_types_select.c
index 99f17bcec8f..b89822a080c 100644
--- a/source/blender/python/bmesh/bmesh_py_types_select.c
+++ b/source/blender/python/bmesh/bmesh_py_types_select.c
@@ -273,9 +273,11 @@ static PyObject *bpy_bmeditselseq_subscript(BPy_BMEditSelSeq *self, PyObject *ke
       const Py_ssize_t len = bpy_bmeditselseq_length(self);
       if (start < 0) {
         start += len;
+        CLAMP_MIN(start, 0);
       }
       if (stop < 0) {
         stop += len;
+        CLAMP_MIN(stop, 0);
       }
     }