Terminal::Dispatcher::dispatch: Initialize map

Fixes this warning (which becomes an error with -Werror):

terminaldispatcher.cpp: In member function ‘void Terminal::Dispatcher::dispatch(Terminal::Function_Type, Parser::Action*, Terminal::Framebuffer*)’:
terminaldispatcher.cpp:156:19: error: ‘map’ may be used uninitialized in this function

Signed-off-by: Anders Kaseorg <andersk@mit.edu>

terminaldispatcher.cpp

@@ -152,7 +152,7 @@ void Dispatcher::dispatch( Function_Type type, Parser::Action *act, Framebuffer
     collect( &act2 ); 
   }
 
-  dispatch_map_t *map;
+  dispatch_map_t *map = NULL;
   switch ( type ) {
   case ESCAPE:  map = &global_dispatch_registry.escape;  break;
   case CSI:     map = &global_dispatch_registry.CSI;     break;