inputsynth: Fix warning about possible uninitialized use

src/inputsynth.c

@@ -41,7 +41,7 @@ _load_library (InputsynthBackend backend)
 
   InputSynth *(*new_func) (void);
 
-  gchar *func_name;
+  gchar *func_name = NULL;
   GString *module_name = g_string_new ("inputsynth_");
   switch (backend)
     {