QByteArray::setRawData(): don't null-terminate initialization from nullptr

it's antithetical to do that, as raw data is documented to be not null-
terminated. QString doesn't, either.

Change-Id: I7ded83a09f64e747a248f9bdac2a364032aae4c0
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/tools/qbytearray.cpp

@@ -4337,7 +4337,6 @@ QByteArray &QByteArray::setRawData(const char *data, uint size)
         } else {
             d->offset = sizeof(QByteArrayData);
             d->size = 0;
-            *d->data() = 0;
         }
     }
     return *this;