common : skip empty implicit default preset (#25643)

The INI parser creates an implicit default section for top-level metadata.
After reserved keys such as `version` are skipped, that section can have no
model options but was still added and exposed in router mode.

Skip only the empty implicit default while preserving real default presets,
named presets, and the global `[*]` settings.

Signed-off-by: JS van Dijk <267467744+hogeheer499-commits@users.noreply.github.com>
Co-authored-by: JS van Dijk <267467744+hogeheer499-commits@users.noreply.github.com>

common/preset.cpp

@@ -330,6 +330,10 @@ common_presets common_preset_context::load_from_ini(const std::string & path, co
             }
         }
 
+        if (preset.name == COMMON_PRESET_DEFAULT_NAME && preset.options.empty()) {
+            continue;
+        }
+
         if (preset.name == "*") {
             // handle global preset
             global = preset;