update elements and fix some bugs

lib/src/prism/plugins/line-numbers/prism-line-numbers.js

-Prism.hooks.add('after-highlight', function (env) {
+(function() {
+
+if (typeof self === 'undefined' || !self.Prism || !self.document) {
+        return;
+}
+
+Prism.hooks.add('complete', function (env) {
+        if (!env.code) {
+                return;
+        }
+
         // works only for <code> wrapped inside <pre> (not inline)
         var pre = env.element.parentNode;
         var clsReg = /\s*\bline-numbers\b\s*/;
         if (
                 !pre || !/pre/i.test(pre.nodeName) ||
-                // Abort only if nor the <pre> nor the <code> have the class
+                        // Abort only if nor the <pre> nor the <code> have the class
                 (!clsReg.test(pre.className) && !clsReg.test(env.element.className))
         ) {
                 return;
         }
 
+        if (env.element.querySelector(".line-numbers-rows")) {
+                // Abort if line numbers already exists
+                return;
+        }
+
         if (clsReg.test(env.element.className)) {
                 // Remove the class "line-numbers" from the <code>
                 env.element.className = env.element.className.replace(clsReg, '');
         }
         if (!clsReg.test(pre.className)) {
                 // Add the class "line-numbers" to the <pre>
                 pre.className += ' line-numbers';
         }
 
-        var linesNum = (1 + env.code.split('\n').length);
+        var match = env.code.match(/\n(?!$)/g);
+        var linesNum = match ? match.length + 1 : 1;
         var lineNumbersWrapper;
 
-        var lines = new Array(linesNum);
+        var lines = new Array(linesNum + 1);
         lines = lines.join('<span></span>');
 
         lineNumbersWrapper = document.createElement('span');
         lineNumbersWrapper.className = 'line-numbers-rows';
         lineNumbersWrapper.innerHTML = lines;
 
         if (pre.hasAttribute('data-start')) {
                 pre.style.counterReset = 'linenumber ' + (parseInt(pre.getAttribute('data-start'), 10) - 1);
         }
 
         env.element.appendChild(lineNumbersWrapper);
 
-});
+});
+
+}());