Avoid exception when MD011/no-reversed-links is not able to report column/length (fixes #339).

lib/md011.js

@@ -20,17 +20,21 @@ module.exports = {
         const line = params.lines[lineNumber - 1];
         const column = unescapeMarkdown(line).indexOf(reversedLink) + 1;
         const length = reversedLink.length;
+        const range = column ? [ column, length ] : null;
+        const fixInfo = column ?
+          {
+            "editColumn": column,
+            "deleteCount": length,
+            "insertText": `[${linkText}](${linkDestination})`
+          } :
+          null;
         addError(
           onError,
           lineNumber,
           reversedLink,
           null,
-          [ column, length ],
-          {
-            "editColumn": column,
-            "deleteCount": length,
-            "insertText": `[${linkText}](${linkDestination})`
-          }
+          range,
+          fixInfo
         );
       }
     });