Fix T63788: Crash if particle system is turned off in particle editing mode

Make sure particle system edit never points to a modifier or particle system
which becomes inactive.

This is needed because copy-on-write will change pointers of them and those
pointers are supposed to be restored from particle system evaluation. But
since the particle system is disabled it never updates pointers.

Reviewers: brecht

Reviewed By: brecht

Differential Revision: https://developer.blender.org/D5180

source/blender/blenkernel/intern/particle.c

@@ -3291,6 +3291,10 @@ void psys_cache_edit_paths(Depsgraph *depsgraph,
   int segments = 1 << pset->draw_step;
   int totpart = edit->totpoint, recalc_set = 0;
 
+  if (edit->psmd_eval == NULL) {
+    return;
+  }
+
   segments = MAX2(segments, 4);
 
   if (!cache || edit->totpoint != edit->totcached) {

source/blender/depsgraph/intern/eval/deg_eval_copy_on_write.cc

@@ -87,6 +87,7 @@ extern "C" {
 #include "BKE_library_query.h"
 #include "BKE_modifier.h"
 #include "BKE_object.h"
+#include "BKE_pointcache.h"
 #include "BKE_sequencer.h"
 #include "BKE_sound.h"
 }
@@ -683,10 +684,22 @@ void set_particle_system_modifiers_loaded(Object *object_cow)
   }
 }
 
+void reset_particle_system_edit_eval(Object *object_cow)
+{
+  LISTBASE_FOREACH (ParticleSystem *, psys, &object_cow->particlesystem) {
+    ParticleSystem *orig_psys = psys->orig_psys;
+    if (orig_psys->edit != NULL) {
+      orig_psys->edit->psys_eval = NULL;
+      orig_psys->edit->psmd_eval = NULL;
+    }
+  }
+}
+
 void update_particles_after_copy(const Object *object_orig, Object *object_cow)
 {
   update_particle_system_orig_pointers(object_orig, object_cow);
   set_particle_system_modifiers_loaded(object_cow);
+  reset_particle_system_edit_eval(object_cow);
 }
 
 void update_pose_orig_pointers(const bPose *pose_orig, bPose *pose_cow)

source/blender/editors/physics/particle_edit.c

@@ -97,23 +97,38 @@ bool PE_poll(bContext *C)
   Object *ob = CTX_data_active_object(C);
 
   if (!scene || !ob || !(ob->mode & OB_MODE_PARTICLE_EDIT)) {
-    return 0;
+    return false;
   }
-  return (PE_get_current(scene, ob) != NULL);
+
+  PTCacheEdit *edit = PE_get_current(scene, ob);
+  if (edit == NULL) {
+    return false;
+  }
+  if (edit->psmd_eval == NULL || edit->psmd_eval->mesh_final == NULL) {
+    return false;
+  }
+
+  return true;
 }
 
 bool PE_hair_poll(bContext *C)
 {
   Scene *scene = CTX_data_scene(C);
   Object *ob = CTX_data_active_object(C);
-  PTCacheEdit *edit;
 
   if (!scene || !ob || !(ob->mode & OB_MODE_PARTICLE_EDIT)) {
-    return 0;
+    return false;
   }
-  edit = PE_get_current(scene, ob);
 
-  return (edit && edit->psys);
+  PTCacheEdit *edit = PE_get_current(scene, ob);
+  if (edit == NULL || edit->psys == NULL) {
+    return false;
+  }
+  if (edit->psmd_eval == NULL || edit->psmd_eval->mesh_final == NULL) {
+    return false;
+  }
+
+  return true;
 }
 
 bool PE_poll_view3d(bContext *C)
@@ -1085,7 +1100,7 @@ static void PE_apply_mirror(Object *ob, ParticleSystem *psys)
   edit = psys->edit;
   psmd_eval = edit->psmd_eval;
 
-  if (!psmd_eval->mesh_final) {
+  if (psmd_eval == NULL || psmd_eval->mesh_final == NULL) {
     return;
   }
 
@@ -1217,7 +1232,7 @@ static void pe_deflect_emitter(Scene *scene, Object *ob, PTCacheEdit *edit)
 
   psys = edit->psys;
 
-  if (!edit->psmd_eval->mesh_final) {
+  if (edit->psmd_eval == NULL || edit->psmd_eval->mesh_final == NULL) {
     return;
   }
 
@@ -1489,7 +1504,7 @@ void update_world_cos(Depsgraph *UNUSED(depsgraph), Object *ob, PTCacheEdit *edi
   KEY_K;
   float hairmat[4][4];
 
-  if (psys == 0 || psys->edit == 0 || psmd_eval->mesh_final == NULL) {
+  if (psys == 0 || psys->edit == 0 || psmd_eval == NULL || psmd_eval->mesh_final == NULL) {
     return;
   }