Fix more Android platform build warnings

engine/source/platformAndroid/AndroidInput.cpp

@@ -411,7 +411,7 @@ const char* Platform::getClipboard()
 //-----------------------------------------------------------------------------
 bool Platform::setClipboard(const char *text)
 {
-	return NULL;//no clipboard on Android
+	return false;//no clipboard on Android
 }
 
 #pragma mark ---- Cursor Functions ----

engine/source/platformAndroid/T2DActivity.cpp

@@ -2678,7 +2678,7 @@ char* _AndroidLoadInternalFile(const char* fn, U32 *size)
 
 	lResult=lJavaVM->AttachCurrentThread(&lJNIEnv, &lJavaVMAttachArgs);
 	if (lResult == JNI_ERR) {
-		return "";
+		return NULL;
 	}
 
 	// Retrieves NativeActivity.