Fix decryption of R=4, V=4 files with < 16-byte keys by 0-padding - undocumented but matches Acrobat behavior (issue #19484)

test/pdfs/.gitignore

@@ -106,6 +106,7 @@
 !issue9084.pdf
 !issue12963.pdf
 !issue9105_reduced.pdf
+!issue19484_2.pdf
 !issue9105_other.pdf
 !issue9252.pdf
 !issue9262_reduced.pdf
@@ -481,6 +482,7 @@
 !openoffice.pdf
 !js-buttons.pdf
 !issue7014.pdf
+!issue19484_1.pdf
 !issue8187.pdf
 !annotation-link-text-popup.pdf
 !issue9278.pdf

test/test_manifest.json

@@ -3629,6 +3629,14 @@
     "link": false,
     "type": "text"
   },
+  {
+    "id": "issue19484_1",
+    "file": "pdfs/issue19484_1.pdf",
+    "md5": "4e9e78a84226dbdddbd735388ccc2dcd",
+    "rounds": 1,
+    "link": false,
+    "type": "eq"
+  },
   {
     "id": "issue5644",
     "file": "pdfs/issue5644.pdf",
@@ -5043,6 +5051,14 @@
     "rounds": 1,
     "type": "eq"
   },
+  {
+    "id": "issue19484_2",
+    "file": "pdfs/issue19484_2.pdf",
+    "md5": "cd3050eda9fa18a7e6a78c702f9890bb",
+    "rounds": 1,
+    "link": false,
+    "type": "eq"
+  },
   {
     "id": "bug894572",
     "file": "pdfs/bug894572.pdf",