Fix default num samples

Author: nikita-malininn

optimum/intel/openvino/quantization.py

@@ -1083,7 +1083,7 @@ def _full_quantization(
     quantized_model = nncf.quantize(
         model,
         calibration_dataset,
-        subset_size=quantization_config.num_samples,
+        subset_size=quantization_config.num_samples if quantization_config.num_samples else 128,
         ignored_scope=quantization_config.get_ignored_scope_instance(),
         model_type=nncf.ModelType(quantization_config.model_type),
         preset=nncf.QuantizationPreset.PERFORMANCE if quantization_config.sym else nncf.QuantizationPreset.MIXED,