Handle the case that no coverage exists for the specified file

Author: dvdoug

src/RawCodeCoverageData.php

@@ -205,6 +205,10 @@ public function removeCoverageDataForFile(string $filename): void
      */
     public function keepCoverageDataOnlyForLines(string $filename, array $lines): void
     {
+        if (!isset($this->lineCoverage[$filename])) {
+            return;
+        }
+
         $this->lineCoverage[$filename] = \array_intersect_key(
             $this->lineCoverage[$filename],
             \array_flip($lines)
@@ -236,6 +240,10 @@ public function removeCoverageDataForLines(string $filename, array $lines): void
             return;
         }
 
+        if (!isset($this->lineCoverage[$filename])) {
+            return;
+        }
+
         $this->lineCoverage[$filename] = \array_diff_key(
             $this->lineCoverage[$filename],
             \array_flip($lines)