[fix](dump) do not report success if dumping fails (#37510)

## Proposed changes
pick #37508

Issue Number: close #xxx

<!--Describe your changes.-->

fe/fe-core/src/main/java/org/apache/doris/catalog/Env.java

@@ -5400,6 +5400,7 @@ public String dumpImage() {
                 saveImage(dumpFile, journalId);
             } catch (IOException e) {
                 LOG.error("failed to dump image to {}", dumpFilePath, e);
+                return null;
             }
         } finally {
             // unlock all