better protection agains generic linear algebra

Author: baggepinnen

src/freqresp.jl

@@ -75,7 +75,8 @@ end
         Q = Matrix(F.Q)
     catch e
         # For matrix types that do not have a hessenberg implementation, we call the standard version of freqresp.
-        e isa MethodError && return freqresp_nohess!(R, sys, w_vec)
+        e isa Union{MethodError, ErrorException} && return freqresp_nohess!(R, sys, w_vec)
+        # ErrorException appears if we try to access Q on a type which does not have Q as a field or property, notably HessenbergFactorization from GenericLinearAlgebra
         rethrow()
     end
     A = F.H

test/test_freqresp.jl

@@ -66,7 +66,7 @@ resp2 = reshape((im*w .+ 2)./(im*w  .+ 1), length(w), 1, 1)
 @inferred freqresp(sys2s, w)
 @inferred freqresp(G2, w)
 @inferred freqresp(H2, w)
-@test @allocated freqresp(sys2, w) < 1.2*305551488 # allow 20% increase due to compiler variations
+@test (@allocated freqresp(sys2, w)) < 1.2*56672 # allow 20% increase due to compiler variations
 
 
 ## Complex-coefficient system