Channel emulator: added input pointer checks

lib/src/phy/channel/channel.cc

@@ -102,8 +102,12 @@ channel::~channel()
 
 void channel::run(cf_t* in[SRSLTE_MAX_PORTS], cf_t* out[SRSLTE_MAX_PORTS], uint32_t len, const srslte_timestamp_t& t)
 {
-
+  // check input pointers
+  if (in != nullptr && out != nullptr) {
+    if (current_srate) {
       for (uint32_t i = 0; i < nof_ports; i++) {
+        // Check buffers are not null
+        if (in[i] != nullptr && out[i] != nullptr) {
           // Copy input buffer
           memcpy(buffer_in, in[i], sizeof(cf_t) * len);
 
@@ -125,6 +129,16 @@ void channel::run(cf_t* in[SRSLTE_MAX_PORTS], cf_t* out[SRSLTE_MAX_PORTS], uint3
           // Copy output buffer
           memcpy(out[i], buffer_in, sizeof(cf_t) * len);
         }
+      }
+    } else {
+      for (uint32_t i = 0; i < nof_ports; i++) {
+        // Check buffers are not null
+        if (in[i] != nullptr && out[i] != nullptr && in[i] != out[i]) {
+          memcpy(out[i], in[i], sizeof(cf_t) * len);
+        }
+      }
+    }
+  }
 }
 
 void channel::set_srate(uint32_t srate)