merge-ort: clean up after failed merge

In 9fefce6 (merge-ort: basic outline for merge_switch_to_result(),
2020-12-13), we added functionality to lay down the result of a merge on
disk. But we forgot to release the data structures in case
`unpack_trees()` failed to run properly.

This was pointed out by the `linux-leaks` job in our CI runs.

Signed-off-by: Johannes Schindelin <[email protected]>

Author: dscho

merge-ort.c

@@ -1002,6 +1002,7 @@ void merge_switch_to_result(struct merge_options *opt,
 		if (checkout(opt, head, result->tree)) {
 			/* failure to function */
 			result->clean = -1;
+			merge_finalize(opt, result);
 			return;
 		}
 
@@ -1010,6 +1011,7 @@ void merge_switch_to_result(struct merge_options *opt,
 						    &opti->conflicted)) {
 			/* failure to function */
 			result->clean = -1;
+			merge_finalize(opt, result);
 			return;
 		}
 	}