fix: returning empty datasourceStucture instead of empty on invalid (#24802)

## Description
> TL;DR now returning empty datasourceStructure object instead of
Mono.empty, also added the analytics call back.

The issue has started in sentry because a snippet has recently been
added to expect some response from server, if the response is empty it
throws error

Fixes #23675

#### Type of change
- Bug fix (non-breaking change which fixes an issue)

#### How Has This Been Tested?
- [x] Manual
- [x] Jest
- [ ] Cypress


## Checklist:
#### Dev activity
- [ ] My code follows the style guidelines of this project
- [ ] I have performed a self-review of my own code
- [ ] I have commented my code, particularly in hard-to-understand areas
- [ ] I have made corresponding changes to the documentation
- [ ] My changes generate no new warnings
- [ ] I have added tests that prove my fix is effective or that my
feature works
- [ ] New and existing unit tests pass locally with my changes
- [ ] PR is being merged under a feature flag


#### QA activity:
- [ ] [Speedbreak
features](https://github.com/appsmithorg/TestSmith/wiki/Guidelines-for-test-plans#speedbreakers-)
have been covered
- [ ] Test plan covers all impacted features and [areas of
interest](https://github.com/appsmithorg/TestSmith/wiki/Guidelines-for-test-plans#areas-of-interest-)
- [ ] Test plan has been peer reviewed by project stakeholders and other
QA members
- [ ] Manually tested functionality on DP
- [ ] We had an implementation alignment call with stakeholders post QA
Round 2
- [ ] Cypress test cases have been added and approved by SDET/manual QA
- [ ] Added `Test Plan Approved` label after Cypress tests were reviewed
- [ ] Added `Test Plan Approved` label after JUnit tests were reviewed

app/server/appsmith-server/src/main/java/com/appsmith/server/solutions/ce/DatasourceStructureSolutionCEImpl.java

@@ -80,7 +80,9 @@ public class DatasourceStructureSolutionCEImpl implements DatasourceStructureSol
                                                   boolean ignoreCache) {
 
         if (Boolean.FALSE.equals(datasourceStorage.getIsValid())) {
-            return Mono.empty();
+            return analyticsService.sendObjectEvent(AnalyticsEvents.DS_SCHEMA_FETCH_EVENT_FAILED,
+                            datasourceStorage, getAnalyticsPropertiesForTestEventStatus(datasourceStorage, false))
+                    .then(Mono.just(new DatasourceStructure()));
         }
 
         Mono<DatasourceStorageStructure> configurationStructureMono = datasourceStructureService

app/server/appsmith-server/src/test/java/com/appsmith/server/solutions/DatasourceStructureSolutionTest.java

@@ -4,6 +4,7 @@ package com.appsmith.server.solutions;
 import com.appsmith.external.models.DBAuth;
 import com.appsmith.external.models.Datasource;
 import com.appsmith.external.models.DatasourceConfiguration;
+import com.appsmith.external.models.DatasourceStorage;
 import com.appsmith.external.models.DatasourceStorageDTO;
 import com.appsmith.external.models.DatasourceStorageStructure;
 import com.appsmith.external.models.DatasourceStructure;
@@ -38,6 +39,7 @@ import org.springframework.util.StringUtils;
 import reactor.core.publisher.Mono;
 import reactor.test.StepVerifier;
 
+import java.util.HashSet;
 import java.util.List;
 
 import static com.appsmith.external.models.DatasourceStructure.TableType.TABLE;
@@ -403,4 +405,30 @@ public class DatasourceStructureSolutionTest {
                 });
     }
 
+
+    @Test
+    @WithUserDetails(value = "api_user")
+    public void verifyEmptyDatasourceStructureObjectIfDatasourceIsInvalid() {
+        DatasourceStorage datasourceStorage = new DatasourceStorage();
+        datasourceStorage.setDatasourceId(datasourceId);
+        datasourceStorage.setEnvironmentId(defaultEnvironmentId);
+        datasourceStorage.setInvalids(new HashSet<>());
+        datasourceStorage.getInvalids().add("random invalid");
+
+        doReturn(Mono.just(datasourceStorage))
+                .when(datasourceStorageService).findByDatasourceAndEnvironmentId(any(), any());
+
+        Mono<DatasourceStructure> datasourceStructureMono =
+                datasourceStructureSolution.getStructure(datasourceId, Boolean.FALSE, defaultEnvironmentId);
+
+        StepVerifier
+                .create(datasourceStructureMono)
+                .assertNext(datasourceStructure -> {
+                    assertThat(datasourceStructure.getTables()).isNull();
+                    assertThat(datasourceStructure.getError()).isNull();
+                })
+                .verifyComplete();
+
+    }
+
 }