Clean up reflog reading error test

Author: srajko

docs/error-handling.md

@@ -128,7 +128,7 @@ The public error API
   bugs, but in the meantime, please code defensively and check for NULL
   when calling this function.
 
-- `void geterr_clear(void)`: This function clears the last error.  The
+- `void giterr_clear(void)`: This function clears the last error.  The
   library will call this when an error is generated by low level function
   and the higher level function handles the error.
 

tests/refs/reflog/reflog.c

@@ -157,12 +157,16 @@ void test_refs_reflog_reflog__reading_the_reflog_from_a_reference_with_no_log_re
 void test_refs_reflog_reflog__reading_a_reflog_with_invalid_format_returns_error(void)
 {
 	git_reflog *reflog;
-	git_error *error;
+	const git_error *error;
+
+	/* clear the error state so we can capture the error generated by git_reflog_read */
+	giterr_clear();
 
 	cl_git_fail(git_reflog_read(&reflog, g_repo, "refs/heads/extra-newline"));
 
 	error = giterr_last();
-	cl_assert(error);
+
+	cl_assert(error != NULL);
 	cl_assert_equal_s("Unable to parse OID - contains invalid characters", error->message);
 }