Generic/EmptyPHPStatement: remove some unreachable code

* Removed two unreachable conditions.
    `$prevNonEmpty` will never be `false` as there will always be
    at least a PHP open tag token before the semicolon token.
* Removed unreachable default case
    `$tokens[$stackPtr]['type']` will always be either `T_SEMICOLON` or
    `T_CLOSE_TAG` as those are the two tokens that this sniff listens for.
    So, the default case will never be reached.

Author: rodrigoprimo

src/Standards/Generic/Sniffs/CodeAnalysis/EmptyPHPStatementSniff.php

@@ -53,10 +53,6 @@ public function process(File $phpcsFile, $stackPtr)
         case 'T_SEMICOLON':
             $prevNonEmpty = $phpcsFile->findPrevious(Tokens::$emptyTokens, ($stackPtr - 1), null, true);
 
-            if ($prevNonEmpty === false) {
-                return;
-            }
-
             if ($tokens[$prevNonEmpty]['code'] !== T_SEMICOLON
                 && $tokens[$prevNonEmpty]['code'] !== T_OPEN_TAG
                 && $tokens[$prevNonEmpty]['code'] !== T_OPEN_TAG_WITH_ECHO
@@ -128,9 +124,8 @@ public function process(File $phpcsFile, $stackPtr)
         case 'T_CLOSE_TAG':
             $prevNonEmpty = $phpcsFile->findPrevious(T_WHITESPACE, ($stackPtr - 1), null, true);
 
-            if ($prevNonEmpty === false
-                || ($tokens[$prevNonEmpty]['code'] !== T_OPEN_TAG
-                && $tokens[$prevNonEmpty]['code'] !== T_OPEN_TAG_WITH_ECHO)
+            if ($tokens[$prevNonEmpty]['code'] !== T_OPEN_TAG
+                && $tokens[$prevNonEmpty]['code'] !== T_OPEN_TAG_WITH_ECHO
             ) {
                 return;
             }
@@ -150,10 +145,6 @@ public function process(File $phpcsFile, $stackPtr)
                 $phpcsFile->fixer->endChangeset();
             }
             break;
-
-        default:
-            // Deliberately left empty.
-            break;
         }//end switch
 
     }//end process()