Fix issues (mis)reported by PHPStan

Author: lkrms

src/Container/Application.php

@@ -637,7 +637,7 @@ private static function doReportTimers(int $level, bool $includeRunning, $types,
             $report[] = implode("\n", $lines);
         }
 
-        if ($report ?? null) {
+        if (isset($report)) {
             Console::print("\n" . implode("\n\n", $report), $level);
         }
     }

src/Curler/Curler.php

@@ -1028,7 +1028,7 @@ protected function execute(bool $close = true, int $depth = 0): string
             $this->close();
         }
 
-        if ($cacheKey ?? null) {
+        if (isset($cacheKey)) {
             Cache::set(
                 $cacheKey,
                 [$this->StatusCode, $this->ReasonPhrase, $this->ResponseHeaders, $this->ResponseBody],
@@ -1246,7 +1246,7 @@ private function process(string $method, ?array $query, $data = null, ?string $m
         if ($this->responseContentTypeIs(MimeType::JSON)) {
             $response = json_decode($this->ResponseBody, $this->ObjectAsArray);
 
-            if ($pager ?? null) {
+            if (isset($pager)) {
                 $response = $pager->getPage($response, $this)->entities();
                 if (array_keys($response) === [0] &&
                         (is_array($response[0]) || is_scalar($response[0]))) {