cgen: fix innermost value of map fixed array (fix #8214) (#8247)

vlib/v/gen/cgen.v

@@ -2005,6 +2005,7 @@ fn (mut g Gen) gen_assign_stmt(assign_stmt ast.AssignStmt) {
 					}
 				}
 			}
+			g.is_assign_lhs = false
 		} else {
 			is_inside_ternary := g.inside_ternary != 0
 			cur_line := if is_inside_ternary && is_decl {

vlib/v/tests/map_complex_fixed_array_test.v

@@ -8,3 +8,12 @@ fn test_complex_map_fixed_array() {
 	println(m)
 	assert '$m' == "{'foo': [[{'bar': 1}, {'baz': 3}]]}"
 }
+
+fn test_innermost_value_of_map_fixed_array() {
+	mut m := map[string][1][2]map[string]int
+	m['foo'] = [[{'bar': 1}, {'baz': 3}]!]!
+	println(m['foo'][0][0]['bar'])
+	println(m['foo'][0][0]['bar'] == 1)
+	assert m['foo'][0][0]['bar'] == 1
+	assert '${m['foo'][0][0]['bar']}' == '1'
+}