Fix readSHP and add a test case

Signed-off-by: William Desportes <williamdes@wdes.fr>

Author: williamdes

src/ShapeFile.php

@@ -660,6 +660,10 @@ public function setError(string $error): void
      */
     public function readSHP(int $bytes)
     {
+        if ($this->shpFile === null) {
+            return false;
+        }
+
         return fread($this->shpFile, $bytes);
     }
 

tests/ShapeFileTest.php

@@ -109,6 +109,16 @@ public function testLoadError(string $filename): void
         $this->assertNotEquals('', $shp->lastError);
     }
 
+    /**
+     * Test load an empty file name
+     */
+    public function testLoadEmptyFilename(): void
+    {
+        $shp = new ShapeFile(1);
+        $shp->loadFromFile('');
+        $this->assertEquals('Not a SHP file (file code mismatch)', $shp->lastError);
+    }
+
     /**
      * Data provider for file loading error tests.
      *