Fix #115924: Sculpt: Draw face sets not working on first try

The ID to draw should start at one, in order to not draw the "1"
face set which displays as white by default. There is still an issue
with dynamic topology drawing, but that's likely unrelated.

source/blender/editors/sculpt_paint/sculpt_face_set.cc

@@ -77,7 +77,7 @@ int find_next_available_id(Object &object)
       const int max = threading::parallel_reduce(
           face_sets.index_range(),
           4096,
-          0,
+          1,
           [&](const IndexRange range, int max) {
             for (const int id : face_sets.slice(range)) {
               max = std::max(max, id);
@@ -94,7 +94,7 @@ int find_next_available_id(Object &object)
       if (cd_offset == -1) {
         return 1;
       }
-      int next_face_set = 0;
+      int next_face_set = 1;
       BMIter iter;
       BMFace *f;
       BM_ITER_MESH (f, &iter, &bm, BM_FACES_OF_MESH) {