Fix index out of bounds for key-value with no value

Fixes spring-atticgh-249

Author: Dave Syer

spring-security-oauth2/src/main/java/org/springframework/security/oauth2/config/annotation/builders/ClientDetailsServiceBuilder.java

@@ -203,7 +203,7 @@ public ClientBuilder additionalInformation(String... pairs) {
 				}
 				int index = pair.indexOf(separator);
 				String key = pair.substring(0, index > 0 ? index : pair.length());
-				String value = index > 0 ? null : pair.substring(index);
+				String value = index > 0 ? pair.substring(index) : null;
 				this.additionalInformation.put(key, (Object) value);
 			}
 			return this;

spring-security-oauth2/src/test/java/org/springframework/security/oauth2/config/annotation/AuthorizationServerConfigurationTests.java

@@ -147,7 +147,7 @@ public void configure(ClientDetailsServiceConfigurer clients) throws Exception {
 		            .authorities("ROLE_CLIENT", "ROLE_TRUSTED_CLIENT")
 		            .scopes("read", "write", "trust")
 		            .accessTokenValiditySeconds(60)
-		            .additionalInformation("foo:bar", "spam:bucket");
+		            .additionalInformation("foo:bar", "spam:bucket", "crap");
 		 	// @formatter:on
 		}