• Replace Optional.of() with Optional.ofNullable() to safely handle null event handlers
• Wrap event handlers in try/finally blocks to guarantee finishTask() execution
• Use Objects.toString() to prevent null task titles from propagating to JavaFX
• Reduce ACTIVE_COLUMNS_MINIMUM from 2 to 1 to keep merge dialog open with single importer

Prevent NPE and guarantee finishTask execution

• Changed Optional.of() to Optional.ofNullable() for three event handlers to safely handle null
 values
• Wrapped each event handler invocation in try/finally blocks to ensure finishTask() always
 executes
• Prevents NullPointerException when event handlers are not set before task registration

jabgui/src/main/java/org/jabref/gui/Notifications.java

Allow merge dialog with single importer result

• Changed ACTIVE_COLUMNS_MINIMUM constant from 2 to 1
• Allows merge dialog to remain open when only one PDF importer returns metadata
• Prevents automatic dialog closure for single-source imports like XMP-only results

jabgui/src/main/java/org/jabref/gui/mergeentries/multiwaymerge/MultiMergeEntriesView.java

Handle null task titles safely in JavaFX

• Replaced direct task.titleProperty().get() with `Objects.toString(task.titleProperty().get(),
 "")`
• Converts null task titles to empty strings instead of propagating null to JavaFX Task
• Prevents null values from reaching the JavaFX task title property

jabgui/src/main/java/org/jabref/gui/util/UiTaskExecutor.java

Description

The new CHANGELOG entry is developer-focused/grammatically incorrect and references #15127 but
links to a different issue (/issues/15283), which can mislead users. This does not meet the
project requirements for user-facing, professional CHANGELOG text with correct references.

Code

CHANGELOG.md[31]

+- We fixed PDF import and prevent NPE in TaskNotification and keep merge dialog open when only one importer succeeds. [#15127](https://github.com/JabRef/jabref/issues/15283)

Evidence

PR Compliance ID 22 requires CHANGELOG entries to be end-user facing, and PR Compliance ID 24
requires user-facing text to be professional/precise and include correct references. The added line
contains technical terms (NPE, TaskNotification) with ungrammatical phrasing (prevent instead
of prevented) and a mismatched issue link target.

AGENTS.md
CHANGELOG.md[31-31]
Best Practice: Learned patterns

Agent prompt

The issue below was found during a code review. Follow the provided context and guidance below and implement a solution

## Issue description
The new `CHANGELOG.md` entry is not user-focused (mentions `NPE`/`TaskNotification`), contains grammatical issues, and the displayed issue reference `#15127` links to `/issues/15283`.
## Issue Context
Compliance requires CHANGELOG entries to be understandable to average users and user-facing text to be precise and correctly referenced.
## Fix Focus Areas
- CHANGELOG.md[31-31]

ⓘ Copy this prompt and use it to remediate the issue with your preferred AI generation tools

Description

TaskNotification now guarantees UI cleanup via finally, but exceptions thrown by preserved
onSucceeded/onFailed/onCancelled handlers are still uncaught and can propagate on the JavaFX UI
thread, potentially triggering uncaught-exception dialogs/log spam.

Code

jabgui/src/main/java/org/jabref/gui/Notifications.java[R76-99]

+            Optional<EventHandler<WorkerStateEvent>> onSucceeded = Optional.ofNullable(task.getOnSucceeded());
           task.setOnSucceeded(event -> {
-                onSucceeded.ifPresent(handler -> handler.handle(event));
-                finishTask();
+                try {
+                    onSucceeded.ifPresent(handler -> handler.handle(event));
+                } finally {
+                    finishTask();
+                }
           });
-            Optional<EventHandler<WorkerStateEvent>> onFailed = Optional.of(task.getOnFailed());
+            Optional<EventHandler<WorkerStateEvent>> onFailed = Optional.ofNullable(task.getOnFailed());
           task.setOnFailed(event -> {
-                onFailed.ifPresent(handler -> handler.handle(event));
-                finishTask();
+                try {
+                    onFailed.ifPresent(handler -> handler.handle(event));
+                } finally {
+                    finishTask();
+                }
           });
-            Optional<EventHandler<WorkerStateEvent>> onCancelled = Optional.of(task.getOnCancelled());
+            Optional<EventHandler<WorkerStateEvent>> onCancelled = Optional.ofNullable(task.getOnCancelled());
           task.setOnCancelled(event -> {
-                onCancelled.ifPresent(handler -> handler.handle(event));
-                finishTask();
+                try {
+                    onCancelled.ifPresent(handler -> handler.handle(event));
+                } finally {
+                    finishTask();
+                }
           });

Evidence

The preserved handlers are invoked without a catch block, and project docs explicitly state these
handlers run on the FX UI thread; thus, any exception thrown in them will occur on the UI thread.

jabgui/src/main/java/org/jabref/gui/Notifications.java[75-99]
jabgui/src/main/java/org/jabref/gui/util/UiTaskExecutor.java[94-96]

Agent prompt

The issue below was found during a code review. Follow the provided context and guidance below and implement a solution

## Issue description
`TaskNotification` ensures `finishTask()` runs, but exceptions thrown by preserved task event handlers still propagate on the JavaFX UI thread.
### Issue Context
This is not a regression from this PR (handlers could throw before too), but since this code is explicitly managing notification UI state, it’s a good choke point to prevent handler exceptions from surfacing as UI-thread uncaught exceptions.
### Fix Focus Areas
- jabgui/src/main/java/org/jabref/gui/Notifications.java[75-99]
- jabgui/src/main/java/org/jabref/gui/Notifications.java[102-108]

ⓘ Copy this prompt and use it to remediate the issue with your preferred AI generation tools