Fix parity bug in egl::Error::createMessageString.
Fix parity bug in egl::Error::createMessageString.

The check should be "==" instead of "!=". This gave a crash any time
we would generate an Error with a message.

Change-Id: I7c5d57e30053591b4713d8c829e89fd1c0703da0
Reviewed-on: https://chromium-review.googlesource.com/244820
Tested-by: Jamie Madill <7e492b4f1c8458024932de3ba475cbf015424c30@chromium.org>
Reviewed-by: Austin Kinross <4e7ea65cff3a7294234757a0f33c94811ce2f382@microsoft.com>
Reviewed-by: Jamie Madill <7e492b4f1c8458024932de3ba475cbf015424c30@chromium.org>

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