Fix exception on link that starts with a space

Author: adam-earthscope

tests/test_urls.py

@@ -46,6 +46,10 @@ def test_urls():
     expect = '\t<p>A link that starts with an h is <a href="/test/">handled</a> incorrectly.</p>'
     assert result == expect
 
+    result = t.parse('A link that starts with a space" raises":/test/ an exception.')
+    expect = '\t<p><a href="/test/">A link that starts with a space&#8221; raises</a> an exception.</p>'
+    assert result == expect
+
 def test_rel_attribute():
     t = Textile(rel='nofollow')
     result = t.parse('"$":http://domain.tld')

textile/core.py

@@ -672,7 +672,10 @@ def markStartOfLinks(self, text):
                             balanced = balanced - 1
                         if re.search(r'\S$', possibility, flags=re.U): # pragma: no branch
                             balanced = balanced + 1
-                        possibility = possible_start_quotes.pop()
+                        try:
+                            possibility = possible_start_quotes.pop()
+                        except IndexError:
+                            break
                     else:
                         # If quotes occur next to each other, we get zero
                         # length strings.  eg. ...""Open the door,