Fix assignment of struct containing array of mappings

test/libsolidity/syntaxTests/memberLookup/memory_structs_with_mapping_array_struct_array.sol

@@ -0,0 +1,12 @@
+contract Test {
+	struct S1 { uint8 a; mapping(uint => uint)[] b1; uint8 c; }
+	struct S2 { uint8 a; S1[] b2; uint8 c; }
+	S2 s2;
+    function f() public {
+        S2 memory x = s2;
+        x.b2.length;
+        x.b2[1].b1[2][3];
+    }
+}
+// ----
+// TypeError: (208-218): Member "b1" is not available in struct Test.S1 memory outside of storage.