[xh123637]

Fixes #12302

What was wrong

In the IntelliJ plugin, pressing End did nothing when Continue's autocomplete had returned a blank suggestion. Repro from the issue:

1. Open any .toml file
2. Type a heading [some_heading<caret>]
3. Press End

Expected: the caret moves to the end of the line. Actual: nothing happens — Continue swallows the keypress even though no suggestion is visible.

Root cause

Two places could produce a blank suggestion, and the platform treats any returned suggestion — even one with an empty gray-text element — as an active suggestion, so its inline-completion handler intercepts End (accept-to-end-of-line) instead of letting the editor handle it:

• ContinueCompletionService.getAutocomplete returned "" (not null) when the core response carried no content, and the provider only checked for null, so it built InlineCompletionSingleSuggestion with an empty InlineCompletionGrayTextElement.
• In the NextEdit path, checkFim can yield an empty fimText when the suggested edit is identical to the existing text, and the provider rendered that as a gray-text suggestion too.

No End-key handling exists in the plugin's own code (verified by searching the whole extensions/intellij tree) — the interception comes from the platform once a suggestion object exists, so the fix is to never surface a blank suggestion.

Changes

• ContinueInlineCompletionProvider.kt: return InlineCompletionSuggestion.Empty when the traditional autocomplete variant is null or blank, and when the NextEdit FIM text is blank.
• ContinueCompletionService.kt: return null instead of "" when the core response has no completion content, so "no completion" is signalled the way the CompletionService contract intends.
• ContinueInlineCompletionProviderTest.kt: two new tests using the issue's exact repro ([some_heading<caret>] + EditorLineEnd): a blank suggestion and a whitespace-only suggestion must both let End move the caret to the end of the line.

Verification

Honest note: I could not run the plugin test suite here — this environment has no JDK at all (and apt-get could not install one), and the IntelliJ tests need the Gradle + IDE sandbox, so the new tests have not been executed and fail-before has not been observed in this environment. The tests follow the existing testInlineCompletion patterns in the same file and exercise the exact repro from the issue; please let CI run them. The fix itself was verified by code inspection: the only two paths that build a gray-text suggestion are now guarded, and getAutocomplete has no other caller besides the provider.

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