Fix for assert when sampling color to non-existent palette

source/blender/blenkernel/BKE_paint.h

@@ -104,6 +104,7 @@ void BKE_paint_reset_overlay_invalid(eOverlayControlFlags flag);
 void BKE_paint_set_overlay_override(enum eOverlayFlags flag);
 
 /* palettes */
+void                 BKE_palette_init(struct Palette *palette);
 void                 BKE_palette_free(struct Palette *palette);
 struct Palette      *BKE_palette_add(struct Main *bmain, const char *name);
 void BKE_palette_copy_data(

source/blender/blenkernel/intern/library.c

@@ -1373,6 +1373,9 @@ void BKE_libblock_init_empty(ID *id)
 			/* Should not be needed - animation from lib pre-2.5 is broken anyway. */
 			BLI_assert(0);
 			break;
+		case ID_PAL:
+			BKE_palette_init((Palette *)id);
+			break;
 		default:
 			BLI_assert(0);  /* Should never reach this point... */
 	}

source/blender/blenkernel/intern/paint.c

@@ -398,10 +398,6 @@ void BKE_palette_clear(Palette *palette)
 Palette *BKE_palette_add(Main *bmain, const char *name)
 {
 	Palette *palette = BKE_id_new(bmain, ID_PAL, name);
-
-	/* enable fake user by default */
-	id_fake_user_set(&palette->id);
-
 	return palette;
 }
 
@@ -430,6 +426,12 @@ void BKE_palette_make_local(Main *bmain, Palette *palette, const bool lib_local)
 	BKE_id_make_local_generic(bmain, &palette->id, true, lib_local);
 }
 
+void BKE_palette_init(Palette *palette)
+{
+	/* Enable fake user by default. */
+	id_fake_user_set(&palette->id);
+}
+
 /** Free (or release) any data used by this palette (does not free the palette itself). */
 void BKE_palette_free(Palette *palette)
 {