🐛 #1600 修复无法切换到初始公众号配置的问题并完善了removeConfigStorage方法

* 修复无法切换到初始公众号配置的问题

* 完善removeConfigStorage

weixin-java-mp/src/main/java/me/chanjar/weixin/mp/api/impl/BaseWxMpServiceImpl.java

@@ -414,7 +414,7 @@ protected String extractAccessToken(String resultContent) throws WxErrorExceptio
 
   @Override
   public void setWxMpConfigStorage(WxMpConfigStorage wxConfigProvider) {
-    final String defaultMpId = WxMpConfigStorageHolder.get();
+    final String defaultMpId = wxConfigProvider.getAppId();
     this.setMultiConfigStorages(ImmutableMap.of(defaultMpId, wxConfigProvider), defaultMpId);
   }
 
@@ -440,6 +440,18 @@ public void addConfigStorage(String mpId, WxMpConfigStorage configStorages) {
   @Override
   public void removeConfigStorage(String mpId) {
     synchronized (this) {
+      if (this.configStorageMap.size() == 1) {
+        this.configStorageMap.remove(mpId);
+        log.warn("已删除最后一个公众号配置：{}，须立即使用setWxMpConfigStorage或setMultiConfigStorages添加配置", mpId);
+        return;
+      }
+      if (WxMpConfigStorageHolder.get().equals(mpId)) {
+        this.configStorageMap.remove(mpId);
+        final String defaultMpId = this.configStorageMap.keySet().iterator().next();
+        WxMpConfigStorageHolder.set(defaultMpId);
+        log.warn("已删除默认公众号配置，公众号【{}】被设为默认配置", defaultMpId);
+        return;
+      }
       this.configStorageMap.remove(mpId);
     }
   }

weixin-java-mp/src/test/java/me/chanjar/weixin/mp/api/impl/BaseWxMpServiceImplTest.java

@@ -41,6 +41,7 @@ public void testSwitchover() {
     assertTrue(this.wxService.switchover("another"));
     assertThat(WxMpConfigStorageHolder.get()).isEqualTo("another");
     assertFalse(this.wxService.switchover("whatever"));
+    assertFalse(this.wxService.switchover("default"));
   }
 
   @Test