fixed warnings in GPU samples

samples/gpu/multi.cpp

@@ -42,10 +42,13 @@ void destroyContexts();
 #define safeCall(expr) safeCall_(expr, #expr, __FILE__, __LINE__)
 inline void safeCall_(int code, const char* expr, const char* file, int line)
 {
-    cout << "CUDA driver API error: code " << code << ", expr " << expr
-        << ", file " << file << ", line " << line << endl;
-    destroyContexts();
-    exit(-1);
+    if (code != CUDA_SUCCESS)
+    {
+        cout << "CUDA driver API error: code " << code << ", expr " << expr
+            << ", file " << file << ", line " << line << endl;
+        destroyContexts();
+        exit(-1);
+    }
 }
 
 // Each GPU is associated with its own context

samples/gpu/stereo_multi.cpp

@@ -44,10 +44,13 @@ void destroyContexts();
 #define safeCall(expr) safeCall_(expr, #expr, __FILE__, __LINE__)
 inline void safeCall_(int code, const char* expr, const char* file, int line)
 {
-    cout << "CUDA driver API error: code " << code << ", expr " << expr
-        << ", file " << file << ", line " << line << endl;
-    destroyContexts();
-    exit(-1);
+    if (code != CUDA_SUCCESS)
+    {
+        cout << "CUDA driver API error: code " << code << ", expr " << expr
+            << ", file " << file << ", line " << line << endl;
+        destroyContexts();
+        exit(-1);
+    }
 }
 
 // Each GPU is associated with its own context