make "Null check used on null value" errors when .so errors out more useful (#1549)

bump monero_c commit to fix enotes error

cw_monero/lib/api/wallet_manager.dart

@@ -21,6 +21,7 @@ final monero.WalletManager wmPtr = Pointer.fromAddress((() {
     print("ptr: $_wmPtr");
   } catch (e) {
     print(e);
+    rethrow;
   }
   return _wmPtr!.address;
 })());

cw_wownero/lib/api/wallet_manager.dart

@@ -21,6 +21,7 @@ final wownero.WalletManager wmPtr = Pointer.fromAddress((() {
     print("ptr: $_wmPtr");
   } catch (e) {
     print(e);
+    rethrow;
   }
   return _wmPtr!.address;
 })());

scripts/prepare_moneroc.sh

@@ -8,7 +8,7 @@ if [[ ! -d "monero_c" ]];
 then
     git clone https://github.com/mrcyjanek/monero_c --branch rewrite-wip
     cd monero_c
-    git checkout d1e246aaf4c53b60ff9e4ab4a4ac3ae4a1f94a33
+    git checkout c094ed5da69d2274747bf6edd7ca24124487bd34
     git reset --hard
     git submodule update --init --force --recursive
     ./apply_patches.sh monero