fix: Better optional deps handling (#353)

odbc and idb-connector are optional deps and  might not be installed.
When either is not available, return an error back to user instead of failing.

Author: abmusse

lib/transports/idbTransport.js

@@ -28,6 +28,11 @@ try {
 }
 
 function idbCall(config, xmlInput, cb) {
+  // idb transport is not available bail out
+  if (idb === null) {
+    cb(new Error('idb-connector was not found, ensure idb-connector is installed properly (idb-connector is only available on IBM i).'), null);
+  }
+
   const {
     database = '*LOCAL',
     username = null,

lib/transports/odbcTransport.js

@@ -28,6 +28,11 @@ try {
 }
 
 function odbcCall(config, xmlInput, done) {
+  // odbc transport is not available bail out
+  if (odbc === null) {
+    done(new Error('odbc transport was not found, ensure odbc is installed properly.'), null);
+  }
+
   const {
     host = 'localhost',
     username = null,