If the Fix it didn't work or you'd rather fix the problem yourself, follow these steps:
First, switch to Desktop mode and unpin the blank shortcuts
With touch, press and hold on the blank shortcut for a few seconds and then release. Tap Unpin this program from taskbar. Do this for each blank icon.
With mouse, right-click each blank icon, and then choose Unpin this program from taskbar.
Now, go back to your Start screen and re-pin each Office RT program to the taskbar
With touch, find the Office program tile, such as Word RT, and swipe down the tile to select it. Tap Pin to taskbar.
With mouse, right-click the Office program tile, such as Word RT, and then click Pin to taskbar.
Now start one of the Office Home and Student 2013 RT programs from the taskbar. The shortcut should appear correctly and you shouldn't receive an error.
When you install the Update for Office Home & Student 2013 RT Preview from Windows Update, the Office taskbar shortcuts in Desktop mode may appear as blank white icons. You may also receive additional errors from the icon for the application shortcut when you try to use it.