corrected bug in convection-diffusion when assigning a FieldVector<1> to a FieldVector<N>

4 jobs for issue/convection_diffusion_bug in 47 minutes and 16 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Test
passed #7977
debian:10 clang-6-libcpp-17

00:29:10

passed #7976
debian:10 gcc-8-17

00:20:57

passed #7978
debian:9 gcc-6-14

00:19:04

passed #7979
ubuntu:18.04 clang-6-17

00:26:15