Explicit null return value in TimechartTransformation.java

[Abigael-JT]

Describe the bug

visitT_timechart_divideByInstruction method explicitly returns null value

Expected behavior

Return value should not be null

How to reproduce

Screenshots

Software version

Desktop (please complete the following information if relevant):

• OS:
• Browser:
• Version:

Additional context

Coverity scan: CID 443509:

[Abigael-JT]

Waiting for PR #490 to be merged first, might fix the issues