Validate avatar uploads

client/views/avatar/avatarPrompt.coffee

@@ -44,8 +44,11 @@ Template.avatarPrompt.events
 
 			template.getSuggestions()
 
-	'change .myFileInput': (event, template) ->
+	'change .avatar-file-input': (event, template) ->
 		FS.Utility.eachFile event, (blob) ->
+			file = new FS.File(blob)
+			if not file? or file.isImage() is false
+				return 
 			reader = new FileReader()
 			reader.readAsDataURL(blob)
 			reader.onloadend = ->

client/views/avatar/avatarPrompt.html

@@ -50,7 +50,7 @@
 								{{/with}}
 								{{#unless upload}}
 									<button type="button" class="button primary">{{_ "avatar.Select_file"}}
-										<input type="file" class="myFileInput">
+										<input type="file" class="avatar-file-input" accept="image/x-png, image/jpeg, image/jpg">
 									</button>
 								{{/unless}}
 							</div>