Do not force palette length to be 256

Author: radarhere

Tests/test_file_gimppalette.py

@@ -32,3 +32,4 @@ def test_get_palette() -> None:
 
     # Assert
     assert mode == "RGB"
+    assert len(palette) / 3 == 11

src/PIL/GimpPaletteFile.py

@@ -27,19 +27,19 @@ class GimpPaletteFile:
     rawmode = "RGB"
 
     def __init__(self, fp: IO[bytes]) -> None:
-        palette = [o8(i) * 3 for i in range(256)]
-
         if not fp.readline().startswith(b"GIMP Palette"):
             msg = "not a GIMP palette file"
             raise SyntaxError(msg)
 
+        palette: list[int] = []
         for i in range(256):
             s = fp.readline()
             if not s:
                 break
 
             # skip fields and comment lines
             if re.match(rb"\w+:|#", s):
+                palette.append(o8(i) * 3)
                 continue
             if len(s) > 100:
                 msg = "bad palette file"
@@ -50,7 +50,7 @@ def __init__(self, fp: IO[bytes]) -> None:
                 msg = "bad palette entry"
                 raise ValueError(msg)
 
-            palette[i] = o8(int(v[0])) + o8(int(v[1])) + o8(int(v[2]))
+            palette.append(o8(int(v[0])) + o8(int(v[1])) + o8(int(v[2])))
 
         self.palette = b"".join(palette)