Fix "PHP Warning: Uninitialized string offset 0"

Author: staabm

src/Metadata/Api/DataProvider.php

@@ -256,7 +256,7 @@ private function dataProvidedByTestWithAnnotation(string $className, string $met
         foreach (explode("\n", $annotationContent) as $candidateRow) {
             $candidateRow = trim($candidateRow);
 
-            if ($candidateRow[0] !== '[') {
+            if ($candidateRow === '' || $candidateRow[0] !== '[') {
                 break;
             }