fix the comment-remover loop

Author: bstorm

adafruit_imageload/pnm/__init__.py

@@ -54,8 +54,12 @@ def load(f, header, *, bitmap=None, palette=None):
 
         next_byte = f.read(1)
         if next_byte == b"#":
-            if next_byte != b"\n":
-                continue
+            while True:
+                f.read(1)
+                if not next_byte:
+                    raise RuntimeError("Unsupported image format")
+                if next_byte != b"\n":
+                    break
         if next_byte.isdigit():
             pnm_header.append(next_byte)
             continue