Generic/UpperCaseConstantName: findNext() may return false

This commit takes into account that `findNext()` may return `false` and
properly handles this case in the modified `if` condition. There were no
issues without this extra check, as when `$constPtr` is `false`,
`$tokens[$constPrt]` evaluates to the first token in the stack and the
first token can never be `T_CONSTANT_ENCAPSED_STRING`, so the sniff
would bail early anyway.

Author: rodrigoprimo

src/Standards/Generic/Sniffs/NamingConventions/UpperCaseConstantNameSniff.php

@@ -110,7 +110,7 @@ public function process(File $phpcsFile, $stackPtr)
 
         // The next non-empty token must be the constant name.
         $constPtr = $phpcsFile->findNext(Tokens::$emptyTokens, ($openBracket + 1), null, true);
-        if ($tokens[$constPtr]['code'] !== T_CONSTANT_ENCAPSED_STRING) {
+        if ($constPtr === false || $tokens[$constPtr]['code'] !== T_CONSTANT_ENCAPSED_STRING) {
             return;
         }
 

src/Standards/Generic/Tests/NamingConventions/UpperCaseConstantNameUnitTest.2.inc

@@ -0,0 +1,7 @@
+<?php
+
+// Intentional parse error (missing constant name).
+// This should be the only test in this file.
+// Testing that the sniff is *not* triggered.
+
+define(