Allow for null values in ExtractingResponseErrorHandler.hasError

This commit fixes the implementation of
ExtractingResponseErrorHandler.hasError to allow for null values,
indicating an override of the behavior inherited from
DefaultResponseErrorHandler.

Issue: SPR-15544

spring-web/src/main/java/org/springframework/web/client/ExtractingResponseErrorHandler.java

@@ -126,9 +126,15 @@ public class ExtractingResponseErrorHandler extends DefaultResponseErrorHandler
 
 	@Override
 	protected boolean hasError(HttpStatus statusCode) {
-		return this.statusMapping.containsKey(statusCode) ||
-				this.seriesMapping.containsKey(statusCode.series()) ||
-						super.hasError(statusCode);
+		if (this.statusMapping.containsKey(statusCode)) {
+			return this.statusMapping.get(statusCode) != null;
+		}
+		else if (this.seriesMapping.containsKey(statusCode.series())) {
+			return this.seriesMapping.get(statusCode.series()) != null;
+		}
+		else {
+			return super.hasError(statusCode);
+		}
 	}
 
 	@Override

spring-web/src/test/java/org/springframework/web/client/ExtractingResponseErrorHandlerTests.java

@@ -68,6 +68,21 @@ public class ExtractingResponseErrorHandlerTests {
 		assertFalse(this.errorHandler.hasError(this.response));
 	}
 
+	@Test
+	public void hasErrorOverride() throws Exception {
+		this.errorHandler.setSeriesMapping(Collections
+				.singletonMap(HttpStatus.Series.CLIENT_ERROR, null));
+
+		given(this.response.getStatusCode()).willReturn(HttpStatus.I_AM_A_TEAPOT);
+		assertTrue(this.errorHandler.hasError(this.response));
+
+		given(this.response.getStatusCode()).willReturn(HttpStatus.NOT_FOUND);
+		assertFalse(this.errorHandler.hasError(this.response));
+
+		given(this.response.getStatusCode()).willReturn(HttpStatus.OK);
+		assertFalse(this.errorHandler.hasError(this.response));
+	}
+
 	@Test
 	public void handleErrorStatusMatch() throws Exception {
 		given(this.response.getStatusCode()).willReturn(HttpStatus.I_AM_A_TEAPOT);
@@ -133,6 +148,7 @@ public class ExtractingResponseErrorHandlerTests {
 	public void handleNoMatchOverride() throws Exception {
 		this.errorHandler.setSeriesMapping(Collections
 				.singletonMap(HttpStatus.Series.CLIENT_ERROR, null));
+
 		given(this.response.getStatusCode()).willReturn(HttpStatus.NOT_FOUND);
 		HttpHeaders responseHeaders = new HttpHeaders();
 		responseHeaders.setContentType(MediaType.APPLICATION_JSON);