Fix for issue #1804 - When tool is a method without parameters, the handling of parameters in ToolSpecification will result in an error. (#1812)

## Issue
Fixes #1804

## Change
Ollama: handling case when tool don`t have parameters.

## General checklist
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[X] -->
- [x] There are no breaking changes
- [x] I have added unit and integration tests for my change
- [x] I have manually run all the unit and integration tests in the
module I have added/changed, and they are all green
- [ ] I have manually run all the unit and integration tests in the
[core](https://github.com/langchain4j/langchain4j/tree/main/langchain4j-core)
and
[main](https://github.com/langchain4j/langchain4j/tree/main/langchain4j)
modules, and they are all green
<!-- Before adding documentation and example(s) (below), please wait
until the PR is reviewed and approved. -->
- [ ] I have added/updated the
[documentation](https://github.com/langchain4j/langchain4j/tree/main/docs/docs)
- [ ] I have added an example in the [examples
repo](https://github.com/langchain4j/langchain4j-examples) (only for
"big" features)
- [ ] I have added/updated [Spring Boot
starter(s)](https://github.com/langchain4j/langchain4j-spring) (if
applicable)

langchain4j-ollama/src/main/java/dev/langchain4j/model/ollama/OllamaMessagesUtils.java

@@ -42,7 +42,7 @@ class OllamaMessagesUtils {
                                 .function(Function.builder()
                                         .name(toolSpecification.name())
                                         .description(toolSpecification.description())
-                                        .parameters(Parameters.builder()
+                                        .parameters(toolSpecification.parameters() == null ? null : Parameters.builder()
                                                 .properties(toolSpecification.parameters().properties())
                                                 .required(toolSpecification.parameters().required())
                                                 .build())

langchain4j-ollama/src/test/java/dev/langchain4j/model/ollama/OllamaToolChatModelIT.java

@@ -20,6 +20,7 @@ import static dev.langchain4j.model.ollama.OllamaImage.TOOL_MODEL;
 import static java.util.Arrays.asList;
 import static java.util.Collections.singletonList;
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
 
 class OllamaToolChatModelIT extends AbstractOllamaToolsLanguageModelInfrastructure {
 
@@ -31,6 +32,11 @@ class OllamaToolChatModelIT extends AbstractOllamaToolsLanguageModelInfrastructu
             .addParameter("location", STRING, description("The location to get the weather for, e.g. San Francisco, CA"))
             .build();
 
+    ToolSpecification toolWithoutParameter = ToolSpecification.builder()
+            .name("get_current_time")
+            .description("Get the current time")
+            .build();
+
     ChatLanguageModel ollamaChatModel = OllamaChatModel.builder()
             .baseUrl(ollama.getEndpoint())
             .modelName(TOOL_MODEL)
@@ -90,4 +96,22 @@ class OllamaToolChatModelIT extends AbstractOllamaToolsLanguageModelInfrastructu
         assertThat(aiMessage.toolExecutionRequests()).isNull();
     }
 
+    @Test
+    void should_handle_tool_without_parameter() {
+
+        // given
+        List<ToolSpecification> toolSpecifications = singletonList(toolWithoutParameter);
+
+        // when
+        List<ChatMessage> chatMessages = singletonList(
+                userMessage("What is the current time?")
+        );
+
+        // then
+        assertDoesNotThrow(() -> {
+            ollamaChatModel.generate(chatMessages, toolSpecifications);
+        });
+
+    }
+
 }