fix: guard CGI Status-line parse in _write_cgi_response

An empty or non-numeric Status: header from git http-backend raised
ValueError/IndexError that escaped the handler thread. Wrap the parse
in a try/except and fall back to HTTP 500 instead.

Closes #254

bot_bottle/git_http_backend.py

@@ -148,7 +148,13 @@ class GitHttpHandler(BaseHTTPRequestHandler):
             key, _, value = line.decode("latin1").partition(":")
             value = value.strip()
             if key.lower() == "status":
-                status = int(value.split()[0])
+                try:
+                    status = int(value.split()[0])
+                except (ValueError, IndexError):
+                    self.log_message(
+                        "malformed CGI Status header %r; using 500", value,
+                    )
+                    status = 500
             else:
                 headers.append((key, value))
         self.send_response(status)