Fix intermittent streaming response aggregation test failure (#4135)

Fix OpenAiChatClientIT.beanStreamOutputConverterRecords test that was failing
intermittently when run as part of a test suite due to empty streaming chunks
causing malformed JSON during aggregation.

Changes:
- Filter out empty/null text chunks before aggregation to prevent malformed JSON
- Replace silent return with explicit test failure when streaming aggregation
  produces empty results
- Add debugging logs to aid troubleshooting of streaming response issues

The test now properly detects and reports streaming aggregation problems
instead of silently skipping, improving CI reliability and error detection.

Auto-cherry-pick to 1.0.x
Fixes #4134

Signed-off-by: Mark Pollack <[email protected]>

Author: markpollack

models/spring-ai-openai/src/test/java/org/springframework/ai/openai/chat/client/OpenAiChatClientIT.java

@@ -56,6 +56,7 @@
 import org.springframework.util.MimeTypeUtils;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.jupiter.api.Assertions.fail;
 
 @SpringBootTest(classes = OpenAiTestConfiguration.class)
 @EnabledIfEnvironmentVariable(named = "OPENAI_API_KEY", matches = ".+")
@@ -235,9 +236,18 @@ void beanStreamOutputConverterRecords() {
 				.stream()
 				.filter(cr -> cr.getResult() != null)
 				.map(cr -> cr.getResult().getOutput().getText())
+				.filter(text -> text != null && !text.trim().isEmpty()) // Filter out empty/null text
 				.collect(Collectors.joining());
 		// @formatter:on
 
+		// Add debugging to understand what text we're trying to parse
+		logger.debug("Aggregated streaming text: {}", generationTextFromStream);
+
+		// Ensure we have valid JSON before attempting conversion
+		if (generationTextFromStream.trim().isEmpty()) {
+			fail("Empty aggregated text from streaming response - this indicates a problem with streaming aggregation");
+		}
+
 		ActorsFilms actorsFilms = outputConverter.convert(generationTextFromStream);
 
 		logger.info("" + actorsFilms);