threads: Assert that the global state is initialized

src/global.c

@@ -64,6 +64,8 @@ git_global_st *git__global_state(void)
 {
 	void *ptr;
 
+	assert(_tls_init);
+
 	if ((ptr = TlsGetValue(_tls_index)) != NULL)
 		return ptr;
 
@@ -105,6 +107,8 @@ git_global_st *git__global_state(void)
 {
 	void *ptr;
 
+	assert(_tls_init);
+
 	if ((ptr = pthread_getspecific(_tls_key)) != NULL)
 		return ptr;