read-cache: free hash context in do_write_index()

While writing an index, a 'git_hash_ctx' is allocated for hashing the
file contents. This should be freed as the method exits.

Signed-off-by: Derrick Stolee <stolee@gmail.com>

Author: derrickstolee

read-cache.c

@@ -3126,6 +3126,7 @@ static int do_write_index(struct index_state *istate, struct tempfile *tempfile,
 		free_hashfile(f);
 	strbuf_release(&sb);
 	free(ieot);
+	free(eoie_c);
 	return ret;
 }