去掉core-fss中server配置项非空要求，没有配置时默认为空白字符串，满足本地部署情况下服务IP不固定要求

Signed-off-by: luoshi <luoshi@qmth.com.cn>

core-fss/src/main/java/com/qmth/boot/core/fss/config/FileStoreProperty.java

@@ -10,7 +10,6 @@ public class FileStoreProperty {
     @NotNull
     private String config;
 
-    @NotNull
     private String server;
 
     public String getConfig() {

core-fss/src/main/java/com/qmth/boot/core/fss/utils/FileStoreBuilder.java

@@ -4,11 +4,12 @@ import com.qmth.boot.core.fss.config.FileStoreProperty;
 import com.qmth.boot.core.fss.store.FileStore;
 import com.qmth.boot.core.fss.store.impl.DiskStore;
 import com.qmth.boot.core.fss.store.impl.OssStore;
+import org.apache.commons.lang3.StringUtils;
 
 public class FileStoreBuilder {
 
     public static FileStore buildFileStore(FileStoreProperty fileStoreProperty) {
-        String server = fileStoreProperty.getServer();
+        String server = StringUtils.trimToEmpty(fileStoreProperty.getServer());
         if (!server.endsWith(FssUtils.FILE_PATH_SEPARATOR)) {
             server = server.concat(FssUtils.FILE_PATH_SEPARATOR);
         }