Add missing arg length check to fix runtime panic

[christophershirk]

This one-line fix addresses a missing constraint error; the ssh <server> repo branch delete command can induce a runtime panic when accessing args[1] if the the branch was not actually specified as an argument.

Repro steps (note: no branch argument specified) ssh soft repo branch delete repofoo

Output (console on server):

2024-07-27 16:23:18 ssh: panic: runtime error: index out of range [0] with length 0
goroutine 934 [running]:
runtime/debug.Stack()
    /usr/local/go/src/runtime/debug/stack.go:24 +0x64
github.com/charmbracelet/wish/recover.MiddlewareWithLogger.func2.1.1.1()
    /Users/user/go/pkg/mod/github.com/charmbracelet/wish@v1.3.2/recover/recover.go:39 +0x44
panic({0x103990940?, 0x140006946c0?})
    /usr/local/go/src/runtime/panic.go:770 +0x124
github.com/charmbracelet/soft-serve/pkg/ssh/cmd.branchCommand.branchDeleteCommand.func3(0x14000bf8c08?, {0x104237940, 0x0, 0x1033d0975?})
    /Users/user/src/soft-serve/pkg/ssh/cmd/branch.go:155 +0x380
github.com/spf13/cobra.(*Command).execute(0x14000bf8c08, {0x104237940, 0x0, 0x0})
    /Users/user/go/pkg/mod/github.com/spf13/cobra@v1.8.0/command.go:983 +0x840
github.com/spf13/cobra.(*Command).ExecuteC(0x140005b3508)
    /Users/user/go/pkg/mod/github.com/spf13/cobra@v1.8.0/command.go:1115 +0x344
github.com/spf13/cobra.(*Command).Execute(...)
    /Users/user/go/pkg/mod/github.com/spf13/cobra@v1.8.0/command.go:1039
github.com/spf13/cobra.(*Command).ExecuteContext(...)
    /Users/user/go/pkg/mod/github.com/spf13/cobra@v1.8.0/command.go:1032
github.com/charmbracelet/soft-serve/pkg/ssh.CommandMiddleware.func1({0x103a114e0, 0x1400066e1a0})
    /Users/user/src/soft-serve/pkg/ssh/middleware.go:145 +0x990
github.com/charmbracelet/soft-serve/pkg/ssh.LoggingMiddleware.func1({0x103a114e0, 0x1400066e1a0})
    /Users/user/src/soft-serve/pkg/ssh/middleware.go:193 +0x630
github.com/charmbracelet/soft-serve/pkg/ssh.NewSSHServer.ContextMiddleware.func3.1({0x103a114e0, 0x1400066e1a0})
    /Users/user/src/soft-serve/pkg/ssh/middleware.go:68 +0x27c
github.com/charmbracelet/soft-serve/pkg/ssh.AuthenticationMiddleware.func1({0x103a114e0, 0x1400066e1a0})
    /Users/user/src/soft-serve/pkg/ssh/middleware.go:54 +0x100
github.com/charmbracelet/wish/recover.MiddlewareWithLogger.func2.1.1({0x103a002a0?, 0x14000774780?}, 0x14000c028a0?, {0x103a114e0?, 0x1400066e1a0?})
    /Users/user/go/pkg/mod/github.com/charmbracelet/wish@v1.3.2/recover/recover.go:43 +0x70
github.com/charmbracelet/wish/recover.MiddlewareWithLogger.func2.1({0x103a114e0, 0x1400066e1a0})
    /Users/user/go/pkg/mod/github.com/charmbracelet/wish@v1.3.2/recover/recover.go:44 +0x48
github.com/charmbracelet/ssh.(*session).handleRequests.func1()
    /Users/user/go/pkg/mod/github.com/charmbracelet/ssh@v0.0.0-20240301204039-e79ff702f5b3/session.go:274 +0x130
created by github.com/charmbracelet/ssh.(*session).handleRequests in goroutine 897
    /Users/user/go/pkg/mod/github.com/charmbracelet/ssh@v0.0.0-20240301204039-e79ff702f5b3/session.go:268 +0x518

Thank you for soft-serve!

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 53.02%. Comparing base (b06b555) to head (3dfcf17). Report is 69 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #568 +/- ## ========================================== + Coverage 51.96% 53.02% +1.06% ========================================== Files 157 159 +2 Lines 13454 11554 -1900 ========================================== - Hits 6991 6127 -864 + Misses 5891 4859 -1032 + Partials 572 568 -4 ```

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[christophershirk]

@aymanbagabas Added test case.

[aymanbagabas]

Thank you, @christophershirk, for noticing and fixing this one!