Fix a check inside render for select elements with ngOptions, which
compares the selected property of an element with it's desired state.
Ensure the placeholder, if available, is explicitly selected if the model
value can not be found in the option list.
Without these fixes it's up to the browser implementation to decide which
option to choose. In most browsers, this has the effect of displaying the
first item in the list. In IE9 however, this causes the select to display
nothing.
Closes#2150, #1826
Bug caused by the use of the `||` operator to replace all non-truthy
values with an empty string. Changed to replace only `undefined` values.
Closes#1401
previously we expected to find option elements only within select element and if
that was not the case we throw an error. This made it impossible to include datalist
element with nested option elements in the template.
Closes#1165
Previously only when ngOptions was used, we correctly handled situations
when model was set to an unknown value. With this change, we'll add/remove
extra unknown option or reuse an existing empty option (option with value
set to "") when model is undefined.
