Fix field resolution not resolving constant value properly

tests/defer.txt

@@ -0,0 +1,11 @@
+a: char;
+
+main :: proc(): int {
+    for i := 0; i < 4; i += 1 {
+        if i == 2 { break; }
+
+        string := &a;
+        defer *string = 1;
+    }
+    return 0;
+}