Fix format overwrite test

A SOS binary had situation were an instruction was being reformatted
as inline data by an extension script.  The code that was supposed
to detect and prevent this had a bug that caused it to only look at
the first byte.  The resulting confusion caused the program to crash.

(issue #150)

SourceGen/CodeAnalysis.cs

@@ -1171,7 +1171,7 @@ namespace SourceGen {
                         " (" + mAnalyzerTags[i] + ")");
                     return false;
                 }
-                if (mAnattribs[offset].IsInstruction) {
+                if (mAnattribs[i].IsInstruction) {
                     LogW(offset, "SIDF rej: not for use with instructions");
                     return false;
                 }