Fix reflection method invokation

Either of Method.invoke, Field.get and Field.set can accept null as
receiver.

Change-Id: I4539dcc95a794f6ee84cf4e7aabf4e8f0206728f

java/src/com/android/inputmethod/compat/CompatUtils.java

@@ -108,7 +108,7 @@ public class CompatUtils {
 
     public static Object invoke(
             Object receiver, Object defaultValue, Method method, Object... args) {
-        if (receiver == null || method == null) return defaultValue;
+        if (method == null) return defaultValue;
         try {
             return method.invoke(receiver, args);
         } catch (IllegalArgumentException e) {
@@ -124,7 +124,7 @@ public class CompatUtils {
     }
 
     public static Object getFieldValue(Object receiver, Object defaultValue, Field field) {
-        if (receiver == null || field == null) return defaultValue;
+        if (field == null) return defaultValue;
         try {
             return field.get(receiver);
         } catch (IllegalArgumentException e) {
@@ -137,7 +137,7 @@ public class CompatUtils {
     }
 
     public static void setFieldValue(Object receiver, Field field, Object value) {
-        if (receiver == null || field == null) return;
+        if (field == null) return;
         try {
             field.set(receiver, value);
         } catch (IllegalArgumentException e) {