Fixes NPE in PersistentPropertyPathExtension.equals.

Closes #1164

spring-data-jdbc/src/test/java/org/springframework/data/jdbc/core/PersistentPropertyPathExtensionUnitTests.java

@@ -200,6 +200,26 @@ public class PersistentPropertyPathExtensionUnitTests {
 		});
 	}
 
+	@Test // GH--1164
+	void equalsWorks() {
+
+		PersistentPropertyPathExtension root1 = extPath(entity);
+		PersistentPropertyPathExtension root2 = extPath(entity);
+		PersistentPropertyPathExtension path1 = extPath("withId");
+		PersistentPropertyPathExtension path2 = extPath("withId");
+
+		assertSoftly(softly -> {
+
+			softly.assertThat(root1).describedAs("root is equal to self").isEqualTo(root1);
+			softly.assertThat(root2).describedAs("root is equal to identical root").isEqualTo(root1);
+			softly.assertThat(path1).describedAs("path is equal to self").isEqualTo(path1);
+			softly.assertThat(path2).describedAs("path is equal to identical path").isEqualTo(path1);
+			softly.assertThat(path1).describedAs("path is not equal to other path").isNotEqualTo(extPath("entityId"));
+			softly.assertThat(root1).describedAs("root is not equal to path").isNotEqualTo(path1);
+			softly.assertThat(path1).describedAs("path is not equal to root").isNotEqualTo(root1);
+		});
+	}
+
 	private PersistentPropertyPathExtension extPath(RelationalPersistentEntity<?> entity) {
 		return new PersistentPropertyPathExtension(context, entity);
 	}

spring-data-relational/src/main/java/org/springframework/data/relational/core/mapping/PersistentPropertyPathExtension.java

@@ -442,7 +442,7 @@ public class PersistentPropertyPathExtension {
 		if (o == null || getClass() != o.getClass()) return false;
 		PersistentPropertyPathExtension that = (PersistentPropertyPathExtension) o;
 		return entity.equals(that.entity) &&
-				path.equals(that.path);
+				Objects.equals(path, that.path);
 	}
 
 	@Override