Bugfix #4872

Posemode, Wkey option "Select constraint target" did not work for Copy
Scale constraint.
Also added a check for NULL pointer, constraint targets cannot exist...

source/blender/blenkernel/intern/constraint.c

@@ -359,6 +359,7 @@ Object *get_constraint_target(bConstraint *con, char **subtarget)
 	case CONSTRAINT_TYPE_SIZELIKE:
 		{
 			bSizeLikeConstraint *data = con->data;
+			*subtarget= data->subtarget;
 			return data->tar;
 		}
 		break;

source/blender/src/poseobject.c

@@ -295,6 +295,7 @@ void pose_select_constraint_target(void)
 					if(ob==target) {
 						if(subtarget) {
 							bPoseChannel *pchanc= get_pose_channel(ob->pose, subtarget);
+							if(pchanc)
 								pchanc->bone->flag |= BONE_SELECTED|BONE_TIPSEL|BONE_ROOTSEL;
 						}
 					}