Do not set Tomcat's trust store password when null

See gh-24041

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/embedded/tomcat/SslConnectorCustomizer.java

@@ -148,7 +148,9 @@ class SslConnectorCustomizer implements TomcatConnectorCustomizer {
 				throw new WebServerException("Could not load trust store: " + ex.getMessage(), ex);
 			}
 		}
-		protocol.setTruststorePass(ssl.getTrustStorePassword());
+		if (ssl.getTrustStorePassword() != null) {
+			protocol.setTruststorePass(ssl.getTrustStorePassword());
+		}
 		if (ssl.getTrustStoreType() != null) {
 			protocol.setTruststoreType(ssl.getTrustStoreType());
 		}

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/web/embedded/tomcat/SslConnectorCustomizerTests.java

@@ -206,6 +206,17 @@ class SslConnectorCustomizerTests {
 		assertThat(protocol.getKeyPass()).isEqualTo("password");
 	}
 
+	@Test
+	void trustStorePasswordIsNotSetWhenNull() {
+		Http11NioProtocol protocol = (Http11NioProtocol) this.tomcat.getConnector().getProtocolHandler();
+		protocol.setTruststorePass("password");
+		Ssl ssl = new Ssl();
+		ssl.setKeyStore("src/test/resources/test.jks");
+		ssl.setTrustStore("src/test/resources/test.jks");
+		new SslConnectorCustomizer(ssl, null).customize(this.tomcat.getConnector());
+		assertThat(protocol.getTruststorePass()).isEqualTo("password");
+	}
+
 	private KeyStore loadStore() throws KeyStoreException, IOException, NoSuchAlgorithmException, CertificateException {
 		KeyStore keyStore = KeyStore.getInstance("JKS");
 		Resource resource = new ClassPathResource("test.jks");