Fixed sign handling in ternary operator

tests/simple/vloghammer.v

@@ -57,3 +57,11 @@ module test08(a, b, y);
   assign y = a == ($signed(b) >>> 1);
 endmodule
 
+module test09(a, b, c, y);
+  input a;
+  input signed [1:0] b;
+  input signed [2:0] c;
+  output [3:0] y;
+  assign y = a ? b : c;
+endmodule
+