fix(lsp): a panic caused by completion with decl_id out of range (#15576)

Fixes a bug caused by #15536 
Sorry about that, @fdncred 

# Description

I've made the panic reproducible in the test case.

TLDR: completer will sometimes return new decl_ids outside of the range
of the engine_state passed in.

# User-Facing Changes

bug fix

# Tests + Formatting

+1

# After Submitting

crates/nu-cli/src/completions/exportable_completions.rs

@@ -69,7 +69,8 @@ impl Completer for ExportableCompletion<'_> {
                     wrapped_name(name),
                     Some(cmd.description().to_string()),
                     None,
-                    SuggestionKind::Command(cmd.command_type(), Some(*decl_id)),
+                    // `None` here avoids arguments being expanded by snippet edit style for lsp
+                    SuggestionKind::Command(cmd.command_type(), None),
                 );
             }
         }