Fixed problems with the prerender

Author: ppham27

src/lib/select/select.spec.ts

@@ -3178,13 +3178,15 @@ class SelectWithGroups {
   @ViewChildren(MdOption) options: QueryList<MdOption>;
 }
 
+
 @Component({
   template: `<form><md-select [(ngModel)]="value"></md-select></form>`
 })
 class InvalidSelectInForm {
   value: any;
 }
 
+
 @Component({
   template: `
     <form [formGroup]="formGroup">

src/lib/select/select.ts

@@ -712,14 +712,10 @@ export class MdSelect extends _MdSelectMixinBase implements AfterContentInit, On
    */
   private _selectValue(value: any, isUserInput = false): MdOption|undefined {
     const optionsArray = this.options.toArray();
-
     const correspondingOption = optionsArray.find((option: MdOption) => {
-      // Treat null as a special reset value.
-      if (option.value === null) {
-        return false;
-      }
       try {
-        return this._compareWith(option.value,  value);
+        // Treat null as a special reset value.
+        return option.value != null && this._compareWith(option.value,  value);
       } catch (error) {
         if (isDevMode()) {
           // Notify developers of errors in their comparator.