public void setFunctionGraphData(FGData data) {
		if (!data.hasResults()) {
			if (reuseCurrentGraph(data)) {
				// leave previous valid function graph visible when the new graph is invalid
				return;
			}
		}
		else {
			cache.put(data.getFunction(), data);
		}

		doSetFunctionGraphData(data);
	}
Signals that something major has changed for the program and we don't know where, so clear
all cached functions for the given program.

BLEH!: I don't like clearing the cache this way...another options is to mark all cached
values as stale, somehow. If we did this, then when the view reuses the cached data, it could
signal to the user that the graph is out-of-date.

@param program the program
Ghidra/Features/FunctionGraph/src/main/java/ghidra/app/plugin/core/functiongraph/mvc/FGController.java