Fix NULL ptr use from dlerror()

hcore/senseApis/senseApiManager.cpp

@@ -65,11 +65,13 @@ SenseApiLib& SenseApiManager::loadSenseApiLib(const std::string& libraryPath)
 
     if (!lib->handle)
     {
-        std::string error = dlerror()
+        const char *dlerr = dlerror();
-            ? dlerror()
+
-            : "Unknown error while opening shlib";
+        std::string error = (dlerr
+            ? dlerr
+            : "Unknown error while opening shlib");
         throw std::runtime_error(
-            std::string(__func__) + " - Cannot load library '"
+            std::string(__func__) + ": Cannot load library '"
             + libraryPath + "': "
             + error);
     }