i3 - improved tiling WM

Bugfix: check symbol for NULL in binding json dump

Patch status: merged

Patch by Tony Crisci

Long description:

When dumping a binding, as is done during the binding event, check
symbol for NULL. If it is, dump json null. This prevents a crash when
running a binding that was configured with bindcode.

fixes #1379

To apply this patch, use:
curl http://cr.i3wm.org/patch/653/raw.patch | git am

b/docs/ipc

19 
@@ -769,9 +769,9 @@ input_code (integer)::
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 	If the binding was configured with +bindcode+, this will be the key code
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 	that was given for the binding. If the binding is a mouse binding, it will be
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 	the number of the mouse button that was pressed. Otherwise it will be 0.
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-symbol (string)::
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+symbol (string or null)::
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 	If this is a keyboard binding that was configured with +bindsym+, this
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-	field will contain the given symbol.
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+	field will contain the given symbol. Otherwise it will be +null+.
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 input_type (string)::
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 	This will be +"keyboard"+ or +"mouse"+ depending on whether or not this was
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 	a keyboard or a mouse binding.

b/src/ipc.c

35 
@@ -160,7 +160,10 @@ static void dump_binding(yajl_gen gen, Binding *bind) {
36 
     ystr((const char*)(bind->input_type == B_KEYBOARD ? "keyboard" : "mouse"));
37
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     ystr("symbol");
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-    ystr(bind->symbol);
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+    if (bind->symbol == NULL)
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+        y(null);
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+    else
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+        ystr(bind->symbol);
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     ystr("command");
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     ystr(bind->command);