Python: Handle loop constructs outside of loops

Observed on some test files in Nuitka/Nuitka, having `break` and
`continue` outside of loops in Python is (to Python) a syntax error, but
our parser happily accepted this broken syntax.

This then caused issues further downstream in the control-flow
construction, as it broke some invariants.

To fix this we now skip the code that would previously fail when the
invariants are broken.

Co-authored-by: yoff <yoff@github.com>

python/ql/test/extractor-tests/syntax_error/without_loop.py

@@ -0,0 +1,10 @@
+# The following constructs are syntax errors in Python, as they are not inside a loop.
+# However, our parser does not consider this code to be syntactically incorrect.
+# Thus, this test is really observing that allowing these constructs does not break any other parts
+# of the extractor.
+
+if True:
+    break
+
+if True:
+    continue