[opt](mtmv) Doesn't throw npe when not set distribution info which should be random (#49402)

### What problem does this PR solve?

pr: https://github.com/apache/doris/pull/39427
commitId: 9ffb060a



Issue Number: close #xxx

Related PR: #xxx

Problem Summary:

### Release note

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    - [ ] Unit Test
    - [ ] Manual test (add detailed scripts or steps below)
    - [ ] No need to test or manual test. Explain why:
- [ ] This is a refactor/code format and no logic has been changed.
        - [ ] Previous test can cover this change.
        - [ ] No code files have been changed.
        - [ ] Other reason <!-- Add your reason?  -->

- Behavior changed:
    - [ ] No.
    - [ ] Yes. <!-- Explain the behavior change -->

- Does this need documentation?
    - [ ] No.
- [ ] Yes. <!-- Add document PR link here. eg:
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fe/fe-core/src/main/java/org/apache/doris/nereids/parser/LogicalPlanBuilder.java

@@ -655,7 +655,12 @@ public class LogicalPlanBuilder extends DorisParserBaseVisitor<Object> {
     }
 
     @Override
-    public CreateMTMVCommand visitCreateMTMV(CreateMTMVContext ctx) {
+    public Command visitCreateMTMV(CreateMTMVContext ctx) {
+        if (ctx.buildMode() == null && ctx.refreshMethod() == null && ctx.refreshTrigger() == null
+                && ctx.cols == null && ctx.keys == null
+                && ctx.HASH() == null && ctx.RANDOM() == null && ctx.BUCKETS() == null) {
+            return new UnsupportedCommand();
+        }
         List<String> nameParts = visitMultipartIdentifier(ctx.mvName);
 
         BuildMode buildMode = visitBuildMode(ctx.buildMode());
@@ -672,7 +677,7 @@ public class LogicalPlanBuilder extends DorisParserBaseVisitor<Object> {
         if (ctx.HASH() != null) {
             desc = new DistributionDescriptor(true, ctx.AUTO() != null, bucketNum,
                     visitIdentifierList(ctx.hashKeys));
-        } else if (ctx.RANDOM() != null) {
+        } else {
             desc = new DistributionDescriptor(false, ctx.AUTO() != null, bucketNum, null);
         }