fix: condition for signalling thread termination is optional

src/backend/threads.c

@@ -59,6 +59,9 @@ static void* pthread_runner (void* thread)
 
   starter->fn (starter->arg);
 
+  if (!starter->finished)
+    return NULL; // no condition var provided for signalling thread termination
+  
   LUMIERA_RECCONDITION_SECTION(cond_sync, starter->finished)
     LUMIERA_RECCONDITION_BROADCAST;
 

src/lib/reccondition.h

@@ -93,7 +93,7 @@
 /**
  * Wait for a condition.
  * Must be used inside a RECCONDITION_SECTION.
- * @param expr Conditon which must become true, else the condition variable goes back into sleep
+ * @param expr Condition which must become true, else the condition variable goes back into sleep
  */
 #define LUMIERA_RECCONDITION_WAIT(expr)                                                                                 \
   do {                                                                                                                  \