Fix GH-13931: Applying zero offset to null pointer in Zend/zend_opcode.c

In the test cases, the compiler bails out due to a fatal error.
The data structures used by the compiler will contain stale values.
In particular, for the test case CG(loop_var_stack) will contain data.
The next compilation will incorrectly use elements from the previous
stack.
To solve this, we reset part of the compiler data structures.
We don't do a full re-initialization via init_compiler() because that will
also reset streams and resources.

Closes GH-13938.

sapi/phpdbg/tests/gh13931.phpt

@@ -0,0 +1,21 @@
+--TEST--
+Applying zero offset to null pointer in Zend/zend_opcode.c
+--FILE--
+<?php
+function foo () {
+    try {
+        break;
+    } finally {
+    }
+}
+foo();
+?>
+--PHPDBG--
+ev 1 + 3
+ev 2 ** 3
+q
+--EXPECTF--
+Fatal error: 'break' not in the 'loop' or 'switch' context in %s on line %d
+prompt> 4
+prompt> 8
+prompt>