Fix: GPv3: Crash rendering cyclic strokes with single point

Creating the batch cache for rendering crashes when
there is a stroke with one point that is set to cyclic.
There was a missing check for the number of points
because we're accessing the curve lengths, which
needs at least 2 points to be populated.

source/blender/draw/intern/draw_cache_impl_grease_pencil.cc

@@ -633,7 +633,7 @@ static void grease_pencil_geom_batch_ensure(Object &object,
                        cols_slice[idx]);
       }
 
-      if (is_cyclic) {
+      if (is_cyclic && points.size() > 1) {
         const int idx = points.size() + 1;
         const float u_stroke = u_scale * lengths[points.size() - 1] + u_translation;
         populate_point(verts_range,