Fix NPE in completion contributor (issue 25711)

The exception occurs because the type can be set to `null` if the element is either a parameter or local variable element. This might be a change since the time this code was originally written.

R=danrubel@google.com

Committed: https://github.com/dart-lang/sdk/commit/bcaedf2b7fbbbb173c47805bbfa3e669d573f673

[Brian Wilkerson, 2016-02-09 20:56:25]

Description was changed from

==========
Fix NPE in completion contributor (issue 25711)

The exception occurs because the type can be set to `null` if a variable
had no explicit type but had it's type inferred.
==========

to

==========
The exception occurs because the type can be set to `null` if the element is
either a parameter or local variable element. This might be a change since the
time this code was originally written.
==========

[Brian Wilkerson, 2016-02-09 21:05:07]

brianwilkerson@google.com changed reviewers:
+ danrubel@google.com

[danrubel, 2016-02-10 17:48:20]

lgtm

[Brian Wilkerson, 2016-02-10 18:49:51]

Description was changed from

==========
The exception occurs because the type can be set to `null` if the element is
either a parameter or local variable element. This might be a change since the
time this code was originally written.
==========

to

==========
The exception occurs because the type can be set to `null` if the element is
either a parameter or local variable element. This might be a change since the
time this code was originally written.

R=danrubel@google.com

Committed:
https://github.com/dart-lang/sdk/commit/bcaedf2b7fbbbb173c47805bbfa3e669d573f673
==========

[Brian Wilkerson, 2016-02-10 18:49:52]

Committed patchset #1 (id:1) manually as
bcaedf2b7fbbbb173c47805bbfa3e669d573f673 (presubmit successful).