[backport] fix assert crash when specified change output spend size is unknown #14851

1. 
   instagibbs commented at 4:07 PM on November 30, 2018: member

   backport of #14380

2. Remove stale comment in CalculateMaximumSignedInputSize 53dcf2b407
3. CreateTransaction: Assume minimum p2sh-p2wpkh spend size for unknown change 2a5cc40dc4
4. instagibbs force-pushed on Nov 30, 2018
5. MarcoFalke added the label Backport on Nov 30, 2018
6. MarcoFalke added this to the milestone 0.17.1 on Nov 30, 2018
7. 
   gmaxwell commented at 6:46 PM on November 30, 2018: contributor

   utACK

8. MarcoFalke merged this on Nov 30, 2018
9. MarcoFalke closed this on Nov 30, 2018

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10. MarcoFalke referenced this in commit 924cf794e1 on Nov 30, 2018
11. MarcoFalke locked this on Sep 8, 2021

Milestone
0.17.1