[CPU] Fix TopK reference implementation to handle NaN inputs correctly

Author: Lagmator22

src/plugins/intel_cpu/src/nodes/topk.cpp

@@ -2511,16 +2511,17 @@ void TopK::topk_ref_process(const float* src_data,
         }
         for (int i2 = 0; i2 < top_k - 1; i2++) {
             for (int i3 = top_k - 1; i3 > i2; i3--) {
-                if (compare(max_values[i3], max_values[i3 - 1])) {
+                if (std::isnan(max_values[i3 - 1]) || compare(max_values[i3], max_values[i3 - 1])) {
                     swap_func(i3, i3 - 1);
                 }
             }
         }
+        // 2. Main Scan Loop
         for (int i2 = top_k; i2 < dim; i2++) {
             max_values[top_k] = src_data[s_index];
             max_indexes[top_k] = i2;
             for (int i3 = top_k; i3 > 0; i3--) {
-                if (compare(max_values[i3], max_values[i3 - 1])) {
+                if (std::isnan(max_values[i3 - 1]) || compare(max_values[i3], max_values[i3 - 1])) {
                     swap_func(i3, i3 - 1);
                 } else {
                     break;