ENH: CLI: fix an exception in CLI testing

when update filament configs, we need to use the old filament variant count
jira: STUDIO-9201

Change-Id: Ibc0084997c264d8527dc9998018907c8af4b2043
(cherry picked from commit 462bfb0b6e941e2771440d8ee06cea149162b595)

src/BambuStudio.cpp

@@ -3032,6 +3032,8 @@ int CLI::run(int argc, char **argv)
                     old_variant_count[k] = old_variant_count[k] + 1;
                 }
             }
+            if (load_filament_count == 0)
+                filament_variant_count = old_variant_count;
         }
         for (int index = 0; index < load_filaments_config.size(); index++) {
             DynamicPrintConfig&  config = load_filaments_config[index];