hashtable: Avoid compiler warning with GCC 12

Even though the assignment of `removed` to `out_row` is tied to the
`found_removed` flag, which is only set if `removed` is set, the
compiler complains that it may be used uninitialized.

src/libstrongswan/collections/hashtable.c

@@ -289,7 +289,7 @@ static inline pair_t *find_key(private_hashtable_t *this, const void *key,
 								u_int *out_hash, u_int *out_row)
 {
 	pair_t *pair;
-	u_int hash, row, p = 0, removed, index;
+	u_int hash, row, p = 0, removed = 0, index;
 	bool found_removed = FALSE;
 
 	if (!this->count && !out_hash && !out_row)