makes testament.nim compiles with --experimental:strictDefs (#26037)

testament/categories.nim

@@ -530,6 +530,7 @@ proc mmRaise(kind: TResultEnum, expected, given: string) =
   raise e
 
 proc isMetamorphicIcTest(content: string): bool =
+  result = false
   for line in content.splitLines:
     if line.strip == "#? metamorphic": return true
 
@@ -561,7 +562,7 @@ proc stableBinary(path: string): string =
   ## so two builds seconds apart differ there even with identical codegen. Skipping
   ## a generous fixed window keeps the clean-vs-incremental check about codegen.
   const headerSkip = 4096
-  var f: File
+  var f: File = nil
   if not open(f, path, fmRead):
     raise newException(IOError, "cannot open: " & path)
   defer: close(f)