Possible overflow in calculations when changing track width of nets

[Alessandro Gatti]

Reproduction steps:

1. Select a net via 'Select trivial connection'.
2. Change the track width with the 'Track & Via properties' dialog. The resulting tracks are totally off-scale, whilst individually changing each track segment width results in a suitably widened track. (See attached images)

System information:

ProductName: Mac OS X
ProductVersion: 10.13.3
BuildVersion: 17D102

KiCad information:

Packaged on 20180316-043049
KiCad revision: r3b0a758
KiCad CMake Settings: -DDEFAULT_INSTALL_PATH=/Library/Application Support/kicad
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Build script revision: r3b0a758

Thank you for your time,
Alessandro