Make getFile consistent with other functions (#298)

* feature: make getFile consistently nullable
closes #287

* build: php 8.1 compatibility

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* build: php 8.1 compatibility

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* feature: make getFile consistently nullable
closes #287

Author: Greg Bowler

src/InputValueGetter.php

@@ -69,14 +69,18 @@ public function getMultipleBool(string $key):array {
 	}
 
 
-	public function getFile(string $key):FileUpload {
+	public function getFile(string $key):?FileUpload {
 		/** @var FileUploadInputData|InputDatum[] $params */
 		$params = $this->fileUploadParameters ?? $this->parameters;
 
-		try {
-			/** @var MultipleInputDatum|FileUpload $file */
-			$file = $params[$key];
+		/** @var MultipleInputDatum|FileUpload|null $file */
+		$file = $params[$key] ?? null;
 
+		if(is_null($file)) {
+			return null;
+		}
+
+		try {
 			if($file instanceof MultipleInputDatum) {
 				return $file->current();
 			}

test/phpunit/InputTest.php

@@ -121,6 +121,12 @@ public function testGetFileFieldSingle(array $get, array $post):void {
 		);
 	}
 
+	public function testGetFile_null():void {
+		$input = new Input([], [], []);
+		$file = $input->getFile("exampleFile");
+		self::assertNull($file);
+	}
+
 	/** @dataProvider dataRandomGetPost */
 	public function testGetInvalidDataType(array $get, array $post):void {
 		self::expectException(InvalidInputMethodException::class);