Fix potential off-by-one in metadata offset

Closes #8009.

To test:

ant -Dtestng.directory=$DATA/sis/ test-automated

components/bio-formats/src/loci/formats/in/SISReader.java

@@ -151,6 +151,11 @@ protected void initStandardMetadata() throws FormatException, IOException {
     short check = in.readShort();
     while (check != 7 && check != 8) {
       check = in.readShort();
+
+      if (check == 0x700 || check == 0x800) {
+        in.skipBytes(1);
+        break;
+      }
     }
     in.skipBytes(4);
 
@@ -176,6 +181,10 @@ protected void initStandardMetadata() throws FormatException, IOException {
       cameraName = channelName.substring(0, length);
     }
 
+    // these are no longer valid
+    getGlobalMetadata().remove("XResolution");
+    getGlobalMetadata().remove("YResolution");
+
     addGlobalMeta("Nanometers per pixel (X)", physicalSizeX);
     addGlobalMeta("Nanometers per pixel (Y)", physicalSizeY);
     addGlobalMeta("Magnification", magnification);