fix(sender): panic when resubmitting failure

[colinlyguo]

Purpose or design rationale of this PR

Fix a bug that would cause panic.

PR title

Your PR title must follow conventional commits (as we are doing squash merge for each PR), so it must start with one of the following types:

• fix: A bug fix

Deployment tag versioning

Has tag in common/version.go been updated or have you added bump-version label to this PR?

• Yes

Breaking change label

Does this PR have the breaking-change label?

• No, this PR is not a breaking change

[codecov]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (6030927) 57.07% compared to head (d4cc0ea) 57.07%.

Files	Patch %	Lines
rollup/internal/controller/sender/sender.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@ Coverage Diff @@## develop #1133 +/- ##
========================================
Coverage 57.07% 57.07% ========================================
Files 150 150 Lines 11203 11203 ========================================
Hits 6394 6394 Misses 4364 4364 Partials 445 445 

Flag	Coverage Δ
rollup	65.92% <0.00%> (ø)

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