Fix potential issues when loading files with missing libraries

This is a continuation of rB39f005eae8eed8b939579aff8c9a05a4f50e5e38

Now all the fields where we check for object type in RNA (like
rna_Curve_object_poll) will have a safe guard for when this isn't the
case.  For example when loading files that has missing object libraries
and all missing objects are replaced with empties (placeholders).

Reviewed By: Brecht

Differential Revision: http://developer.blender.org/D5425

1 files changed, 10 insertions, 2 deletions

diff --git a/source/blender/editors/object/object_constraint.c b/source/blender/editors/object/object_constraint.c
index c780ae4cf8c..14813f9a936 100644
--- a/source/blender/editors/object/object_constraint.c
+++ b/source/blender/editors/object/object_constraint.c
@@ -493,8 +493,12 @@ static void test_constraint(
                CONSTRAINT_TYPE_CLAMPTO,
                CONSTRAINT_TYPE_SPLINEIK)) {
         if (ct->tar) {
+          /* The object type check is only needed here in case we have a placeholder
+           * object assigned (because the library containing the curve is missing).
+           *
+           * In other cases it should be impossible to have a type missmatch.
+           */
           if (ct->tar->type != OB_CURVE) {
-            ct->tar = NULL;
             con->flag |= CONSTRAINT_DISABLE;
           }
           else {
@@ -507,8 +511,12 @@ static void test_constraint(
       }
       else if (con->type == CONSTRAINT_TYPE_ARMATURE) {
         if (ct->tar) {
+          /* The object type check is only needed here in case we have a placeholder
+           * object assigned (because the library containing the armature is missing).
+           *
+           * In other cases it should be impossible to have a type missmatch.
+           */
           if (ct->tar->type != OB_ARMATURE) {
-            ct->tar = NULL;
             con->flag |= CONSTRAINT_DISABLE;
           }
           else if (!BKE_armature_find_bone_name(BKE_armature_from_object(ct->tar),