Validate input_char in MatchStaticString.match()
Microvm.rx_char() returns '' when there is nothing to read,
so we need to make sure we bail out to avoid advancing the
input window.
@@ -24,6 +24,8 @@ class MatchStaticString:
Preserve built `_input` if partially matches `_string`.
Return True when `_input` is the same as `_string`.
"""
+ if input_char == '':
+ return False
self._input += str(input_char)
if self._input == self._string[:len(self._input)]:
if len(self._input) == len(self._string):
