CodeGen bug: "Variable `LLFALL` has not been defined", even when it is a top-level transient array with a symbolic shape.

[pratyai]

This is the smallest graph that I came up with for demo: https://polybox.ethz.ch/index.php/s/E9QxXiTLjaFfezR

In the JSON file, the LLFALL is defined at the top level as follows:

{
  "type": "SDFG",
  "attributes": {
    "name": "loop1_test_function",
    "_arrays": {

... truncated ...

      "LLFALL": {
        "type": "Array",
        "attributes": {
          "strides": [
            "1"
          ],
          "total_size": "NCLV",
          "offset": [
            "-1"
          ],
          "optional": false,
          "shape": [
            "NCLV"
          ],
          "transient": true,
          "debuginfo": null
        }
      },

... truncated ...

Furthermore:

• While codegen throws the error while processing the state _state_l15_c15, if I remove the other branch, the compilation succeeds.
• If I apply simplify on the original graph that I started with, the compilation succeeds too. But it produces C++ code with undefined behaviour. (Not sure if I can reproduce that for this clipped graph, but I think that's not very important since compile() should produce correct code for correct graph without any further transforms anyway).

If the input graph is wrong for some reason, please let me know.