Added safeguard for deranged one-line scripts.

Should never ever happen, of course, but somewhere in the universe exists a
distutils script with just the `#!bin/python` line... Added a len() to guard
against that.

src/zc/buildout/easy_install.py

@@ -1050,7 +1050,7 @@ def _distutils_script(path, dest, script_content, initialization, rsetup):
         return []
     source_encoding_line = ''
     original_content = ''.join(lines[1:])
-    if is_source_encoding_line(lines[1]):
+    if (len(lines) > 1) and is_source_encoding_line(lines[1]):
         # The second line contains a source encoding line. Copy it verbatim.
         source_encoding_line = lines[1].rstrip()
         original_content = ''.join(lines[2:])