Give custom message in about page when liblo/osc is not enabled

Signed-off-by: falkTX <falktx@falktx.com>

source/backend/CarlaStandalone.cpp

@@ -2232,7 +2232,7 @@ const char* carla_get_host_osc_url_tcp(CarlaHostHandle handle)
     static const char* const notAvailable = "(OSC TCP port not available)";
     return notAvailable;
 #else
-    return gNullCharPtr;
+    return "(OSC support not available in this build)";
 
     // unused
     (void)handle;
@@ -2260,7 +2260,7 @@ const char* carla_get_host_osc_url_udp(CarlaHostHandle handle)
     static const char* const notAvailable = "(OSC UDP port not available)";
     return notAvailable;
 #else
-    return gNullCharPtr;
+    return "(OSC support not available in this build)";
 
     // unused
     (void)handle;