refactor($parse): improve readability on conditional assignment

Use logical OR operator instead of if statement

Closes #5065

Author: dimirc

src/ng/parse.js

@@ -361,11 +361,7 @@ Lexer.prototype = {
           string += String.fromCharCode(parseInt(hex, 16));
         } else {
           var rep = ESCAPE[ch];
-          if (rep) {
-            string += rep;
-          } else {
-            string += ch;
-          }
+          string = string + (rep || ch);
         }
         escape = false;
       } else if (ch === '\\') {