Fix NullPointerException with Ollama + tool calls

Fixed #1459

models/spring-ai-ollama/src/main/java/org/springframework/ai/ollama/OllamaChatModel.java

@@ -211,13 +211,18 @@ public class OllamaChatModel extends AbstractToolCallSupport implements ChatMode
 
 			Flux<ChatResponse> chatResponse = ollamaResponse.map(chunk -> {
 				String content = (chunk.message() != null) ? chunk.message().content() : "";
-				List<AssistantMessage.ToolCall> toolCalls = chunk.message().toolCalls() == null ? List.of()
-						: chunk.message()
-							.toolCalls()
-							.stream()
-							.map(toolCall -> new AssistantMessage.ToolCall("", "function", toolCall.function().name(),
-									ModelOptionsUtils.toJsonString(toolCall.function().arguments())))
-							.toList();
+
+				List<AssistantMessage.ToolCall> toolCalls = List.of();
+
+				// Added null checks to prevent NPE when accessing tool calls
+				if (chunk.message() != null && chunk.message().toolCalls() != null) {
+					toolCalls = chunk.message()
+						.toolCalls()
+						.stream()
+						.map(toolCall -> new AssistantMessage.ToolCall("", "function", toolCall.function().name(),
+								ModelOptionsUtils.toJsonString(toolCall.function().arguments())))
+						.toList();
+				}
 
 				var assistantMessage = new AssistantMessage(content, Map.of(), toolCalls);
 

models/spring-ai-ollama/src/test/java/org/springframework/ai/ollama/OllamaChatModelMultimodalIT.java

@@ -40,6 +40,7 @@ import java.io.IOException;
 import java.util.List;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.Assert.assertThrows;
 
 @SpringBootTest
 @Testcontainers
@@ -67,6 +68,18 @@ class OllamaChatModelMultimodalIT extends BaseOllamaIT {
 	@Autowired
 	private OllamaChatModel chatModel;
 
+	@Test
+	void unsupportedMediaType() throws IOException {
+
+		var imageData = new ClassPathResource("/norway.webp");
+
+		var userMessage = new UserMessage("Explain what do you see on this picture?",
+				List.of(new Media(MimeTypeUtils.IMAGE_PNG, imageData)));
+
+		assertThrows(RuntimeException.class, () -> chatModel.call(new Prompt(List.of(userMessage))));
+
+	}
+
 	@Test
 	void multiModalityTest() throws IOException {