Fix (unreported) Invalid clearing handling in IDP_ResizeIDPArray.

This function would only call `IDP_FreePropertyContent` on the items it
is releasing from its buffer, when reducing the length of the array.

However, it needs to call `IDP_ClearProperty` instead, otherwise some
invalid 'dirty' data is kept in the released properties, e.g. the `len`
value for groups or arrays.

Not sure how this never bit us before, but the recent asserts added by
6cb2226f13 did trigger in that case, once the code was re-using these
released IDProps.

Pull Request: https://projects.blender.org/blender/blender/pulls/146326

source/blender/blenkernel/intern/idprop.cc

@@ -158,7 +158,7 @@ void IDP_ResizeIDPArray(IDProperty *prop, int newlen)
   if (newlen <= prop->totallen) {
     if (newlen < prop->len && prop->totallen - newlen < IDP_ARRAY_REALLOC_LIMIT) {
       for (int i = newlen; i < prop->len; i++) {
-        IDP_FreePropertyContent(GETPROP(prop, i));
+        IDP_ClearProperty(GETPROP(prop, i));
       }
 
       prop->len = newlen;
@@ -174,7 +174,7 @@ void IDP_ResizeIDPArray(IDProperty *prop, int newlen)
   if (newlen < prop->len) {
     /* newlen is smaller */
     for (int i = newlen; i < prop->len; i++) {
-      IDP_FreePropertyContent(GETPROP(prop, i));
+      IDP_ClearProperty(GETPROP(prop, i));
     }
   }