do not pass NULL to cudaFreeHost

Compared to cudaFree, which allows passing 0 as C free() (noop),
the documantation for cudaFreeHost states that:
"Frees the memory space pointed to by hostPtr, which must have been
returned by a previous call to cudaMallocHost() or cudaHostAlloc()."

So ensure that this is true (although there is no evidence that there
were any problems with `cudaFreeHost(0)`).

Author: MartinPulec

src/gpujpeg_decoder.c

@@ -336,7 +336,9 @@ gpujpeg_decoder_decode(struct gpujpeg_decoder* decoder, uint8_t* image, size_t i
         coder->data_raw_allocated_size = 0;
 
         // (Re)allocate raw data in host memory
-        cudaFreeHost(coder->data_raw);
+        if ( coder->data_raw != NULL ) {
+            cudaFreeHost(coder->data_raw);
+        }
         coder->data_raw = NULL;
         cudaMallocHost((void**)&coder->data_raw, coder->data_raw_size * sizeof(uint8_t));
         // (Re)allocate raw data in device memory

src/utils/image_delegate.c

@@ -92,6 +92,9 @@ gpujpeg_cuda_realloc_sized_host(void* ptr, int oldsz, int newsz);
 static void
 gpujpeg_cuda_free_host(void* ptr)
 {
+    if ( ptr == NULL ) {
+        return;
+    }
     GPUJPEG_CHECK_EX(cudaFreeHost(ptr), "Could not free host pointer", );
 }