constify missing catch cases

- ensure all missing catch cases are constant where possible

src/bitcoin-cli.cpp

@@ -94,7 +94,7 @@ static bool AppInitRPC(int argc, char* argv[])
     // Check for -testnet or -regtest parameter (BaseParams() calls are only valid after this clause)
     try {
         SelectBaseParams(ChainNameFromCommandLine());
-    } catch(std::exception &e) {
+    } catch (const std::exception& e) {
         fprintf(stderr, "Error: %s\n", e.what());
         return false;
     }