Fix typing problems in OC_Image

Signed-off-by: Côme Chilliet <come.chilliet@nextcloud.com>

Author: come-nc

lib/private/legacy/OC_Image.php

@@ -125,7 +125,11 @@ public function mimeType() {
 	 * @return int
 	 */
 	public function width() {
-		return $this->valid() ? imagesx($this->resource) : -1;
+		if ($this->valid() && (($width = imagesx($this->resource)) !== false)) {
+			return $width;
+		} else {
+			return -1;
+		}
 	}
 
 	/**
@@ -134,7 +138,11 @@ public function width() {
 	 * @return int
 	 */
 	public function height() {
-		return $this->valid() ? imagesy($this->resource) : -1;
+		if ($this->valid() && (($height = imagesy($this->resource)) !== false)) {
+			return $height;
+		} else {
+			return -1;
+		}
 	}
 
 	/**

lib/public/IImage.php

@@ -99,7 +99,7 @@ public function show($mimeType = null);
 	public function save($filePath = null, $mimeType = null);
 
 	/**
-	 * @return resource|\GdImage Returns the image resource in any.
+	 * @return false|resource|\GdImage Returns the image resource if any
 	 * @since 8.1.0
 	 */
 	public function resource();