minirst: don't choke on empty text

mercurial/minirst.py

@@ -38,6 +38,7 b' def findblocks(text):'
     blocks = []
     for b in _blockre.split(text.lstrip('\n').rstrip()):
         lines = b.splitlines()
+        if lines:
         indent = min((len(l) - len(l.lstrip())) for l in lines)
         lines = [l[indent:] for l in lines]
         blocks.append(dict(indent=indent, lines=lines))