Fix the showCondition could be null

src/main/java/io/jenkins/plugins/localization_zh_cn/CommunityDecorator.java

@@ -38,6 +38,11 @@ public class CommunityDecorator extends PageDecorator {
         }
 
         String conditionName = communityProperty.getShowCondition();
+        if(conditionName == null) {
+            // when this plugin just be installed without restart, could be under this situation
+            return isCurrentLanguage;
+        }
+
         UserCommunityProperty.ShowConditions condition =
                 UserCommunityProperty.ShowConditions.valueOf(conditionName);
         switch (condition) {

src/main/java/io/jenkins/plugins/localization_zh_cn/UserCommunityProperty.java

@@ -10,7 +10,7 @@ import org.kohsuke.stapler.DataBoundSetter;
 import javax.annotation.Nonnull;
 
 public class UserCommunityProperty extends UserProperty {
-    private String showCondition;
+    private String showCondition = ShowConditions.Chinese.name();
 
     @DataBoundConstructor
     public UserCommunityProperty(){}