Fix csstext not outputting the liniar angle that was parsed

[Fraaankes]

Types of Changes

Bugfix

Prerequisites

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• I have read the CONTRIBUTING document
• My code follows the code style of this project

Contribution Type

What types of changes does your code introduce? Put an x in all the boxes that apply:

• Bug fix (non-breaking change which fixes an issue, issue: linear-gradients are not written to css with angles #45 )
• New feature (non-breaking change which adds functionality, make sure to open an associated issue first)
• Breaking change (fix or feature that would cause existing functionality to change)
• My change requires a change to the documentation
• I have updated the documentation accordingly
• I have added tests to cover my changes
• All new and existing tests passed

Description

Fix an off-by-1 error causing the angle to get overridden in args and output the correct angle for "known" values.

[claassistantio]

All committers have signed the CLA.

[FlorianRappl]

LGTM! Thanks!