Protect against null strings in hal wrapper implementation.

Some HALs may provide null pointers in lieu of empty strings.
Avoid simple copies of these strings.

Bug: 35384551
Test: Verify affected device (Pixel-C) boots and auto-rotate works.
Change-Id: I37ab6e781d6dfdcc1667bcc0467690f7c2c9a557
diff --git a/sensors/1.0/default/convert.cpp b/sensors/1.0/default/convert.cpp
index 306d3a3..748a963 100644
--- a/sensors/1.0/default/convert.cpp
+++ b/sensors/1.0/default/convert.cpp
@@ -25,8 +25,8 @@
 namespace implementation {
 
 void convertFromSensor(const sensor_t &src, SensorInfo *dst) {
-    dst->name = src.name;
-    dst->vendor = src.vendor;
+    dst->name = src.name == nullptr ? "" : src.name;
+    dst->vendor = src.vendor == nullptr ? "" : src.vendor;
     dst->version = src.version;
     dst->sensorHandle = src.handle;
     dst->type = (SensorType)src.type;
@@ -36,8 +36,8 @@
     dst->minDelay = src.minDelay;
     dst->fifoReservedEventCount = src.fifoReservedEventCount;
     dst->fifoMaxEventCount = src.fifoMaxEventCount;
-    dst->typeAsString = src.stringType;
-    dst->requiredPermission = src.requiredPermission;
+    dst->typeAsString = src.stringType == nullptr ? "" : src.stringType;
+    dst->requiredPermission = src.requiredPermission == nullptr ? "" : src.requiredPermission;
     dst->maxDelay = src.maxDelay;
     dst->flags = src.flags;
 }