Handle blank lines of < 6 chars.

Also emit a better warning for bad lines - identify the line number.

plugin/cobol.py

@@ -47,7 +47,7 @@ def cobol_Renumber():
 
   # Look for gaps.
   for i in xrange(len(lines)):
-    if len(lines[i]) == 0 or lines[i][:6] == '      ':
+    if len(lines[i]) == 0 or lines[i][:6].isspace():
       if not gap:
         gap['i'] = i
         gap['last_line_no'] = last_line_no
@@ -55,7 +55,7 @@ def cobol_Renumber():
       try:
         last_line_no = int(lines[i][:6])
       except ValueError:
-          print('Malformed line - has non-numbers in columns 1-6')
+          print('Malformed line (%d) - has non-numbers in columns 1-6' % i - 1)
           return
       if gap:
         delta = math.floor((last_line_no - gap['last_line_no']) /