空指针保护

mpmaster/src/main/java/com/xypower/mpmaster/MainActivity.java

@@ -184,7 +184,12 @@ public class MainActivity extends AppCompatActivity {
         MicroPhotoContext.AppConfig appConfig = MicroPhotoContext.getMpAppConfig(context);
         StringBuilder stringBuilder = new StringBuilder();
         if (TextUtils.isEmpty(appConfig.cmdid)) {
-            stringBuilder.append("CMDID：" + SysApi.getSerialNo(getApplicationContext()) + " (SN)");
+            String sn = SysApi.getSerialNo(getApplicationContext());
+            if (TextUtils.isEmpty(sn)) {
+                stringBuilder.append("CMDID：");
+            } else {
+                stringBuilder.append("CMDID：" + sn + " (SN)");
+            }
          } else {
             stringBuilder.append("CMDID：" + appConfig.cmdid);
         }