Raster fix for dials.stills_process (#2128)

* Fix raster scans for dials.stills_process

Two specific fixes:
- In _determine_max_memory_needed, check if the scan is a still, in which case its bbox z coordinates should be 0, 1
- In dials.import, in the manual geometry updater, fix convert_sequences_to_stills. This was likely fallout from cctbx/dxtbx#438, where the imageset indices were redone to use less memory.

Fixes #2127

Co-authored-by: James Beilsten-Edmands <jbeilstenedmands@gmail.com>

newsfragments/2128.bugfix

@@ -0,0 +1 @@
+``dials.stills_process`` could crash for raster scans of stills.

src/dials/algorithms/integration/integrator.py

@@ -1234,13 +1234,10 @@ def _determine_max_memory_needed(experiments, reflections):
                     for j, experiment in enumerate(experiments):
                         if experiment.imageset == imageset:
                             subset.extend(reflections.select(reflections["id"] == j))
-                try:
-                    if imageset.get_scan():
-                        frame0, frame1 = imageset.get_scan().get_array_range()
-                    else:
-                        raise RuntimeError
-                except RuntimeError:  # catch DXTBX_ASSERT if no scan in imageset
+                if not imageset.get_scan() or imageset.get_scan().is_still():
                     frame0, frame1 = (0, len(imageset))
+                else:
+                    frame0, frame1 = imageset.get_scan().get_array_range()
                 flatten = self.params.integration.integrator == "flat3d"
                 max_needed = max(
                     max_memory_needed(subset, frame0, frame1, flatten),

src/dials/command_line/dials_import.py

@@ -352,7 +352,7 @@ def __call__(self, imageset):
 
         if self.params.geometry.convert_sequences_to_stills:
             imageset = ImageSetFactory.imageset_from_anyset(imageset)
-            for j in imageset.indices():
+            for j in range(len(imageset)):
                 imageset.set_scan(None, j)
                 imageset.set_goniometer(None, j)
         if not isinstance(imageset, ImageSequence):