Fix getContentsAsync() with invalid characters

chrome/content/zotero/xpcom/file.js

@@ -210,9 +210,9 @@ Zotero.File = new function(){
 		
 		var options = {
 			charset: charset ? charset : "UTF-8",
-			// This doesn't seem to work -- reading an image file still throws NS_ERROR_ILLEGAL_INPUT
-			replacement: "\uFFFD"
+			replacement: 65533
 		};
+		
 		var deferred = Zotero.Promise.defer();
 		NetUtil.asyncFetch(source, function(inputStream, status) {
 			if (!Components.isSuccessCode(status)) {

test/tests/data/invalidChar.txt

@@ -0,0 +1 @@
+A®B

test/tests/data/utf8Char.txt

@@ -0,0 +1 @@
+A犬B

test/tests/fileTest.js

@@ -4,6 +4,22 @@ describe("Zotero.File", function () {
 			var path = OS.Path.join(getTestDataDirectory().path, "empty");
 			assert.equal((yield Zotero.File.getContentsAsync(path)), "");
 		})
+		
+		it("should handle an extended character", function* () {
+			var contents = yield Zotero.File.getContentsAsync(
+				OS.Path.join(getTestDataDirectory().path, "utf8Char.txt")
+			);
+			assert.lengthOf(contents, 3);
+			assert.equal(contents, "A\u72acB");
+		})
+		
+		it("should handle an invalid character", function* () {
+			var contents = yield Zotero.File.getContentsAsync(
+				OS.Path.join(getTestDataDirectory().path, "invalidChar.txt")
+			);
+			assert.lengthOf(contents, 3);
+			assert.equal(contents, "A\uFFFDB");
+		})
 	})
 	
 	describe("#copyDirectory()", function () {