user32: Avoid crashing if we can't alloc text buffer

[Nikolay Sivov]

On 12/3/2011 04:35, Bruno Jesus wrote:

> If LocalLock fails the buffer is not allocated and get_text_length, which is used in several different places, will make wine crash.
LocalLock doesn't allocate anything. You need to figure out why buffer 
is not allocated at this point.