Bug in source-1-with-copying-gc.js where environment extension count is sometimes very large

[btzy]

Steps to reproduce:

1. Load source-1-with-copying-gc.js into Source Academy
2. Replace the examples at the bottom with the test case below
3. Add the following these two lines before the EXTEND() in M[CALL] (line 1384 on GitHub / line 1379 in Source Academy):

   display(A, "env ext count:");
   display(N, "OS size:");

4. Run the code

Test case

initialize_machine(448);
P = parse_and_compile("                                     \
function recurse(x, y, operation, initvalue) {              \
    return y === 0                                          \
        ? initvalue                                         \
        : operation(x, recurse(x, y - 1,                    \
                    operation, initvalue));                 \
}                                                           \
                                                            \
function f(x, z) { return x * z; }                          \
recurse(2, 2, f, 1);                                        ");
//print_program(P);
run();

Actual output

Running VM with heap size: 448
env ext count: 5
OS size: 5
env ext count: 17
OS size: 7
env ext count: 17
OS size: 7
env ext count: 17
OS size: 7
env ext count: 17
OS size: 2
Flip! FREE: 220
env ext count: 314
OS size: 2
result: heap node of type = number, value = 4 ""
undefined

Expected The env ext count in the output above should be much less than 314.

[martin-henz]

The EXTEND macro expects the old environment (environment to be extended) in Register A. So 314 is the address of an environment.