Fix check gpu index logic in local mode (#3163)

ts/nni_manager/training_service/local/gpuScheduler.ts

@@ -58,12 +58,12 @@ class GPUScheduler {
         return [];
     }
 
-    public getSystemGpuCount(): number {
+    public getSystemGpuCount(): number | undefined{
         if (this.gpuSummary !== undefined) {
             return this.gpuSummary.gpuCount;
         }
 
-        return 0;
+        return undefined;
     }
 
     public async stop(): Promise<void> {

ts/nni_manager/training_service/local/localTrainingService.ts

@@ -435,8 +435,8 @@ class LocalTrainingService implements TrainingService {
     }
 
     private checkSpecifiedGpuIndices(): void {
-        const gpuCount: number = this.gpuScheduler.getSystemGpuCount();
-        if (this.designatedGpuIndices !== undefined) {
+        const gpuCount: number | undefined = this.gpuScheduler.getSystemGpuCount();
+        if (this.designatedGpuIndices !== undefined && gpuCount !== undefined) {
             for (const index of this.designatedGpuIndices) {
                 if (index >= gpuCount) {
                     throw new Error(`Specified GPU index not found: ${index}`);