fix: TypeError: Cannot read property 'errorCount' of undefined

Without this patch, there are situations when the .solhintignore file
causes all inputs files being ignored. This is a problem because the
'reports' variable ends up being an empty array, and therefore
reports[0] is undefined.

This patch solves the problem by checking that reports array exists and
has a length greater than 0.

Thanks to Adam Spiers (@aspiers) who originally discovered a bug.

Issue-URL: https://bytemeta.vip/repo/protofire/solhint/issues/239

solhint.js

@@ -94,7 +94,13 @@ function execMainAction() {
   }
 
   if (printReports(reports, formatterFn)) {
-    if (program.maxWarnings && !reports[0].errorCount && warningsNumberExceeded) {
+    if (
+      program.maxWarnings &&
+      reports &&
+      reports.length > 0 &&
+      !reports[0].errorCount &&
+      warningsNumberExceeded
+    ) {
       console.log(
         'Solhint found more warnings than the maximum specified (maximum: %s)',
         program.maxWarnings