SCI: Inhibit spurious GCC warnings in script patching code.

The two relevant variables upon inspection of the current code should
not be used uninitialized as per the compiler linter warning, but
removing this by adding a zero initialization is simple.
It is also good practice and should prevent future issues if the code
is modified.

engines/sci/engine/script_patches.cpp

@@ -2668,8 +2668,8 @@ void ScriptPatcher::initSignature(const SciScriptPatcherEntry *patchTable, bool
 	uint16 curWord;
 	uint16 curCommand;
 	uint32 curValue;
-	byte byte1;
-	byte byte2;
+	byte byte1 = 0;
+	byte byte2 = 0;
 	int patchEntryCount = 0;
 
 	// Count entries and allocate runtime data