Allow compilation of empty string

Fixes #461

dist/handlebars.js

@@ -2079,7 +2079,7 @@ JavaScriptCompiler.isValidJavaScriptVariableName = function(name) {
 };
 
 Handlebars.precompile = function(input, options) {
-  if (!input || (typeof input !== 'string' && input.constructor !== Handlebars.AST.ProgramNode)) {
+  if (input == null || (typeof input !== 'string' && input.constructor !== Handlebars.AST.ProgramNode)) {
     throw new Handlebars.Exception("You must pass a string or Handlebars AST to Handlebars.precompile. You passed " + input);
   }
 
@@ -2093,7 +2093,7 @@ Handlebars.precompile = function(input, options) {
 };
 
 Handlebars.compile = function(input, options) {
-  if (!input || (typeof input !== 'string' && input.constructor !== Handlebars.AST.ProgramNode)) {
+  if (input == null || (typeof input !== 'string' && input.constructor !== Handlebars.AST.ProgramNode)) {
     throw new Handlebars.Exception("You must pass a string or Handlebars AST to Handlebars.compile. You passed " + input);
   }
 

lib/handlebars/compiler/compiler.js

@@ -1238,7 +1238,7 @@ JavaScriptCompiler.isValidJavaScriptVariableName = function(name) {
 };
 
 Handlebars.precompile = function(input, options) {
-  if (!input || (typeof input !== 'string' && input.constructor !== Handlebars.AST.ProgramNode)) {
+  if (input == null || (typeof input !== 'string' && input.constructor !== Handlebars.AST.ProgramNode)) {
     throw new Handlebars.Exception("You must pass a string or Handlebars AST to Handlebars.precompile. You passed " + input);
   }
 
@@ -1252,7 +1252,7 @@ Handlebars.precompile = function(input, options) {
 };
 
 Handlebars.compile = function(input, options) {
-  if (!input || (typeof input !== 'string' && input.constructor !== Handlebars.AST.ProgramNode)) {
+  if (input == null || (typeof input !== 'string' && input.constructor !== Handlebars.AST.ProgramNode)) {
     throw new Handlebars.Exception("You must pass a string or Handlebars AST to Handlebars.compile. You passed " + input);
   }