Fix regression...

IPython/core/inputtransformer2.py

@@ -636,7 +636,7 b' class TransformerManager:'
                 MemoryError, SyntaxWarning):
             return 'invalid', None
         else:
-            if not lines[-1].strip().endswith(':'):
+            if len(lines) > 1 and not lines[-1].strip().endswith(':'):
                 return 'incomplete', find_last_indent(lines)
         return 'complete', None