Smoke test: In collections, log an error if reserve() is called with a number smaller than the current size. Don't log an error if it is called with a number smaller than the current capacity.

core/templates/hash_map.h

@@ -432,6 +432,7 @@ public:
 	// Reserves space for a number of elements, useful to avoid many resizes and rehashes.
 	// If adding a known (possibly large) number of elements at once, must be larger than old capacity.
 	void reserve(uint32_t p_new_capacity) {
+		ERR_FAIL_COND_MSG(p_new_capacity < size(), "reserve() called with a capacity smaller than the current size. This is likely a mistake.");
 		uint32_t new_index = capacity_index;
 
 		while (hash_table_size_primes[new_index] < p_new_capacity) {