Fixed: Don't crash if GL_VERSION returns NULL (it should never happen)

--HG--
branch : develop

code/nel/src/3d/driver/opengl/driver_opengl_extension.cpp

@@ -1567,11 +1567,20 @@ void	registerGlExtensions(CGlExtensions &ext)
 
 	// OpenGL 1.2 ??
 	const char	*nglVersion = (const char *)glGetString (GL_VERSION);
+
+	if (nglVersion)
+	{
 		sint a = 0, b = 0;
 
 		// 1.2***  ???
 		sscanf(nglVersion, "%d.%d", &a, &b);
 		ext.Version1_2 = (a==1 && b>=2) || (a>=2);
+	}
+	else
+	{
+		nlwarning("3D: Unable to get GL_VERSION, OpenGL 1.2 should be supported on all recent GPU...");
+		ext.Version1_2 = true;
+	}
 
 	const char *vendor = (const char *) glGetString (GL_VENDOR);
 	const char *renderer = (const char *) glGetString (GL_RENDERER);