fix: Avoid total failure on wasm finalizer call

Author: ldemailly

targets/wasm_exec.js

@@ -303,9 +303,22 @@
 
 					// func finalizeRef(v ref)
 					"syscall/js.finalizeRef": (v_ref) => {
-						// Note: TinyGo does not support finalizers so this should never be
-						// called.
-						console.error('syscall/js.finalizeRef not implemented');
+						// Note: TinyGo does not support finalizers so this is only called
+						// for one specific case, by js.go:jsString. and can/might leak memory.
+						const id = mem().getUint32(unboxValue(v_ref), true);
+						// Note that this if is so far seemingly never true. Someone should investigate why.
+						if (this._goRefCounts?.[id] !== undefined) {
+							this._goRefCounts[id]--;
+							if (this._goRefCounts[id] === 0) {
+								const v = this._values[id];
+								this._values[id] = null;
+								this._ids.delete(v);
+								this._idPool.push(id);
+							}
+						} else {
+							// Log as a hint and reminder that something is probably off.
+							console.log("syscall/js.finalizeRef: unknown id", id);
+						}
 					},
 
 					// func stringVal(value string) ref