linux-pulseaudio: Check for failed operations

Add checks to make sure the pulseaudio operation objects are actually
valid and the request did not fail right away. Other pulseaudio
functions dealing with the objects expect them not to be NULL,
otherwise they will kill the application with a failing assert.

plugins/linux-pulseaudio/pulse-wrapper.c

@@ -172,6 +172,10 @@ int_fast32_t pulse_get_source_info_list(pa_source_info_cb_t cb, void* userdata)
 
 	pa_operation *op = pa_context_get_source_info_list(
 		pulse_context, cb, userdata);
+	if (!op) {
+		pulse_unlock();
+		return -1;
+	}
 	while (pa_operation_get_state(op) == PA_OPERATION_RUNNING)
 		pulse_wait();
 	pa_operation_unref(op);
@@ -191,6 +195,10 @@ int_fast32_t pulse_get_source_info(pa_source_info_cb_t cb, const char *name,
 
 	pa_operation *op = pa_context_get_source_info_by_name(
 		pulse_context, name, cb, userdata);
+	if (!op) {
+		pulse_unlock();
+		return -1;
+	}
 	while (pa_operation_get_state(op) == PA_OPERATION_RUNNING)
 		pulse_wait();
 	pa_operation_unref(op);
@@ -209,6 +217,10 @@ int_fast32_t pulse_get_server_info(pa_server_info_cb_t cb, void* userdata)
 
 	pa_operation *op = pa_context_get_server_info(
 		pulse_context, cb, userdata);
+	if (!op) {
+		pulse_unlock();
+		return -1;
+	}
 	while (pa_operation_get_state(op) == PA_OPERATION_RUNNING)
 		pulse_wait();
 	pa_operation_unref(op);