Fix failing test (after previous commit)

spring-web/src/main/java/org/springframework/http/server/reactive/DefaultPathSegmentContainer.java

@@ -190,10 +190,14 @@ class DefaultPathSegmentContainer implements PathSegmentContainer {
 	}
 
 	static PathSegmentContainer subPath(PathSegmentContainer container, int fromIndex, int toIndex) {
+		if (fromIndex == toIndex) {
+			return EMPTY_PATH;
+		}
 		List<PathSegment> segments = container.pathSegments();
 		if (fromIndex == 0 && toIndex == segments.size()) {
 			return container;
 		}
+
 		Assert.isTrue(fromIndex < toIndex, "fromIndex: " + fromIndex + " should be < toIndex " + toIndex);
 		Assert.isTrue(fromIndex >= 0 && fromIndex < segments.size(), "Invalid fromIndex: " + fromIndex);
 		Assert.isTrue(toIndex >= 0 && toIndex <= segments.size(), "Invalid toIndex: " + toIndex);

spring-web/src/test/java/org/springframework/http/server/reactive/DefaultRequestPathTests.java

@@ -36,6 +36,9 @@ public class DefaultRequestPathTests {
 		// no context path
 		testRequestPath("/a/b/c", "", "/a/b/c", false, true, false);
 
+		// context path only
+		testRequestPath("/a/b", "/a/b", "", false, true, false);
+
 		// empty path
 		testRequestPath("", "", "", true, false, false);
 		testRequestPath("", "/", "", true, false, false);