Cleanup: redundant initialization

These were limited to obvious cases. Some less obvious cases
were kept as refactoring might make them necessary in future.

source/blender/blenkernel/intern/mesh_evaluate.c

@@ -2567,7 +2567,7 @@ bool BKE_mesh_center_median_from_polys(const Mesh *me, float r_cent[3])
   const MLoop *mloop = me->mloop;
   const MVert *mvert = me->mvert;
   zero_v3(r_cent);
-  for (mpoly = me->mpoly; i--; mpoly++) {
+  for (; i--; mpoly++) {
     int loopend = mpoly->loopstart + mpoly->totloop;
     for (int j = mpoly->loopstart; j < loopend; j++) {
       add_v3_v3(r_cent, mvert[mloop[j].v].co);