Revert "Use empty string for hidl_string instead of doing memset to 0."

This reverts commit 1764f648a56ab5b71d82a7488f0b9dd0da78cc6c.

Bug: 35104859
Test: Build
Change-Id: I2a62ef0a9d71cd6f8b85075d32051bff08c5790b
(cherry picked from commit 30a0e4a94a1be693963b51dc24ea53457e76522d)
diff --git a/libril/ril_service.cpp b/libril/ril_service.cpp
index 72b2123..d01beb0 100644
--- a/libril/ril_service.cpp
+++ b/libril/ril_service.cpp
@@ -2462,7 +2462,6 @@
         populateResponseInfo(responseInfo, serial, responseType, e);
         LastCallFailCauseInfo info;
         memset(&info, 0, sizeof(info));
-        info.vendorCause = hidl_string();
         if (response == NULL) {
             RLOGE("radio::getCurrentCallsResponse Invalid response: NULL");
             if (e == RIL_E_SUCCESS) responseInfo.error = RadioError::INVALID_RESPONSE;
@@ -2660,7 +2659,6 @@
         RLOGE("Invalid response: NULL");
         if (e == RIL_E_SUCCESS) responseInfo.error = RadioError::INVALID_RESPONSE;
         memset(&result, 0, sizeof(result));
-        result.ackPDU = hidl_string();
     } else {
         RIL_SMS_Response *resp = (RIL_SMS_Response *) response;
         result.messageRef = resp->messageRef;
@@ -2719,7 +2717,8 @@
         RLOGE("Invalid response: NULL");
         if (e == RIL_E_SUCCESS) responseInfo.error = RadioError::INVALID_RESPONSE;
         memset(&result, 0, sizeof(result));
-        result.simResponse = hidl_string();
+        hidl_string emptyString;
+        result.simResponse = emptyString;
     } else {
         RIL_SIM_IO_Response *resp = (RIL_SIM_IO_Response *) response;
         result.sw1 = resp->sw1;