fix error with empty rowsupport in. broadcast (#341)

Author: dlfivefifty

Project.toml

@@ -1,6 +1,6 @@
 name = "BandedMatrices"
 uuid = "aae01518-5342-5314-be14-df237901396f"
-version = "0.17.16"
+version = "0.17.17"
 
 [deps]
 ArrayLayouts = "4c555306-a7a7-4459-81d9-ec55ddd5c99a"

src/generic/broadcast.jl

@@ -693,7 +693,7 @@ function checkzerobands(dest, f, (A,B)::NTuple{2,AbstractMatrix})
 
     rspA = rowsupport(A)
     rspB = rowsupport(B)
-    for j = min(minimum(rspA), minimum(rspB)):max(maximum(rspA), maximum(rspB))
+    for j = min(first(rspA), first(rspB)):max(last(rspA), last(rspB))
         for k = max(1,j-u) : min(j-d_u-1,m)
             iszero(f(A[k,j], B[k,j])) || throw(BandError(dest,b))
         end

test/test_broadcasting.jl

@@ -706,5 +706,9 @@ import BandedMatrices: BandedStyle, BandedRows
         copyto!(A, Z)
         copyto!(B, Z)
         @test A == B == zeros(5,5)
+
+        a = BandedMatrix(Zeros(0,4), (-1,1))
+        b = BandedMatrix(Zeros(0,4), (-1,2))
+        @test a-b == a
     end
 end