Bug in erosion outputs

[dvalters]

Problem

• If I try to input one grainsize only, the output still gives me a volume of sediment for all 9 grain sizes.

[dvalters]

• possibly not a bug. further tests to be done to confirm and follow up (may just have been an issue with .o files needing deleting by running make clean first before recompiling.

[dvalters]

Update: seems to have solved the issue now by recompiling.

My own test gave me zeros in all the sediment values but could be just because velocity/shear stress wasn't high enough to pick up or deposit that particular hard coded grain size in the short run Boscaslte test. Maggie's test seems to be working now anyway and she is getting singular values for the d1 grain size when d2-d9 are set to 0.0 for their respective proportions in the dprop[11] grain proportion array. (And recompile after clearing the old .o object files) (See also #40, but not essential to implement this)