Fix issues identified by Psalm

Author: sebastianbergmann

.psalm/baseline.xml

@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<files psalm-version="3.11.1@8533b866ab1a46e5a69a4692ff57f10529dbfbeb">
+<files psalm-version="3.11.4@58e1d8e68e5098bf4fbfdfb420c38d563f882549">
   <file src="src/CodeCoverage.php">
     <ArgumentTypeCoercion occurrences="2">
       <code>$unit[0]</code>
@@ -81,12 +81,6 @@
     <ArgumentTypeCoercion occurrences="1">
       <code>$this-&gt;nodes[$this-&gt;position]</code>
     </ArgumentTypeCoercion>
-    <InvalidNullableReturnType occurrences="1">
-      <code>AbstractNode</code>
-    </InvalidNullableReturnType>
-    <NullableReturnStatement occurrences="1">
-      <code>$this-&gt;valid() ? $this-&gt;nodes[$this-&gt;position] : null</code>
-    </NullableReturnStatement>
   </file>
   <file src="src/Report/Xml/BuildInformation.php">
     <PossiblyNullReference occurrences="1">

src/Node/Iterator.php

@@ -56,7 +56,7 @@ public function key(): int
     /**
      * Returns the current element.
      */
-    public function current(): AbstractNode
+    public function current(): ?AbstractNode
     {
         return $this->valid() ? $this->nodes[$this->position] : null;
     }

src/Report/Crap4j.php

@@ -38,7 +38,7 @@ public function process(CodeCoverage $coverage, ?string $target = null, ?string
 
         $project = $document->createElement('project', \is_string($name) ? $name : '');
         $root->appendChild($project);
-        $root->appendChild($document->createElement('timestamp', \date('Y-m-d H:i:s', $_SERVER['REQUEST_TIME'])));
+        $root->appendChild($document->createElement('timestamp', (string) \date('Y-m-d H:i:s', $_SERVER['REQUEST_TIME'])));
 
         $stats       = $document->createElement('stats');
         $methodsNode = $document->createElement('methods');

src/Report/Html/Facade.php

@@ -60,7 +60,7 @@ public function process(CodeCoverage $coverage, string $target): void
             $_SERVER['REQUEST_TIME'] = \time();
         }
 
-        $date = \date('D M j G:i:s T Y', $_SERVER['REQUEST_TIME']);
+        $date = (string) \date('D M j G:i:s T Y', $_SERVER['REQUEST_TIME']);
 
         $dashboard = new Dashboard(
             $this->templatePath,

src/Report/Text.php

@@ -274,10 +274,13 @@ private function printCoverageCounts(int $numberOfCoveredElements, int $totalNum
         \sprintf($format, $totalNumberOfElements) . ')';
     }
 
-    private function format($color, $padding, $string): string
+    /**
+     * @param false|string $string
+     */
+    private function format(string $color, int $padding, $string): string
     {
         $reset = $color ? self::COLOR_RESET : '';
 
-        return $color . \str_pad($string, $padding) . $reset . \PHP_EOL;
+        return $color . \str_pad((string) $string, $padding) . $reset . \PHP_EOL;
     }
 }

src/Report/Xml/Report.php

@@ -72,13 +72,13 @@ public function getSource(): Source
         return new Source($source);
     }
 
-    private function setName($name): void
+    private function setName(string $name): void
     {
         $this->getContextNode()->setAttribute('name', \basename($name));
         $this->getContextNode()->setAttribute('path', \dirname($name));
     }
 
-    private function getUnitObject($tagName, $name): Unit
+    private function getUnitObject(string $tagName, $name): Unit
     {
         $node = $this->getContextNode()->appendChild(
             $this->getDomDocument()->createElementNS(