Fix #95400: Crash when running Euler Filter on baked Curves

Fix a crash when using the Euler Filter from the Graph Editor on baked curves.

The crash happened because baked curves have no bezt array.
Skipping any curves where that was missing fixes the issue.

Co-authored-by: Christoph Lendenfeld <chris.lenden@gmail.com>
Pull Request #104858

source/blender/editors/space_graph/graph_edit.c

@@ -1880,6 +1880,11 @@ static bool euler_filter_single_channel(FCurve *fcu)
     return false;
   }
 
+  /* Skip baked FCurves. */
+  if (fcu->bezt == NULL) {
+    return false;
+  }
+
   /* `prev` follows bezt, bezt = "current" point to be fixed. */
   /* Our method depends on determining a "difference" from the previous vert. */
   bool is_modified = false;